SCons: Use CPPDEFINES instead of CPPFLAGS for pre-processor defines

It's the recommended way to set those, and is more portable
(automatically prepends -D for GCC/Clang and /D for MSVC).

We still use CPPFLAGS for some pre-processor flags which are not
defines.

Added a fallback size to the lightmap baker in case mesh lightmap hint sizes are 0,0

Implement snapping in the CSG gizmos and 3D polygon editor

Make the AndroidManifest meta-data name attribute settable. 

AppVeyor: Skip saving cache on non-master branches

ConnectionsDock: Add tooltip with signal description

Tilemap fix displaced textures and shapes and added center texture and compatibility mode

Fix editor crash when StreamPeerSSL is unavilable.

Fix various memory leaks and errors

Add "Go To" menu to the script editor and move the bookmark and breakpoint menus there

The spatial editor snap settings will now affect the CSG gizmos
and 3D polygon editor (which is used in CSGPolygon).

Otherwise we run into situations where commits to stable branches
induce very long build times, as they have to basically build from
scratch but also invalidate the cache for future commits on the
master branch.

This commit also makes the cache folder branch-specific, but since
it's still limited to 1 GB of total cache size, we don't enable it
for non-master, as we would still run into issues with non-master
build invalidating the master cache.

This commit fix #22989 #15249 #28206. Main problem is that tilemap displace textures in different tile origins in a strange way and doesn´t respect coincidence between texture and shapes in not uniform tiles. This issue is present in godot 3.0 and godot 3.1. To maintain compatibility are added a compatibility mode and a center texture option. Other related issues and pull request: #28896 #29487 #29519 #29961. Idications of #30204 are added

Had to create a custom Tree to override `make_custom_control` for the
rich text display, similar to EditorProperty.

Fixes #30244.

Use GCC 9 in travis.

The fix for EditorNode is a bit hacky, but the handling of the buttons
and features there is hacky too (based on enums that might not reflect
the actual state).

CryptoCore class to access to base crypto utils.

Fix few GCC9 warnings:

thirdparty/assimp/include/assimp/material.inl: In member function 'aiReturn aiMaterial::Get(const char*, unsigned int, unsigned int, aiColor3D&) const':
thirdparty/assimp/include/assimp/material.inl:176:33: error: implicitly-declared 'aiColor3D& aiColor3D::operator=(const aiColor3D&)' is deprecated [-Werror=deprecated-copy]
  176 |     pOut = aiColor3D(c.r,c.g,c.b);

modules/dds/texture_loader_dds.cpp:167:50: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
  167 |  if (format_flags & DDPF_FOURCC && format_fourcc == PF_FOURCC("DXT1")) {
      |                                                  ^
[ 28%] modules/dds/texture_loader_dds.cpp:170:57: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
  170 |  } else if (format_flags & DDPF_FOURCC && format_fourcc == PF_FOURCC("DXT3")) {
      |                                                         ^
modules/dds/texture_loader_dds.cpp:174:57: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
  174 |  } else if (format_flags & DDPF_FOURCC && format_fourcc == PF_FOURCC("DXT5")) {
      |                                                         ^
modules/dds/texture_loader_dds.cpp:177:57: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
  177 |  } else if (format_flags & DDPF_FOURCC && format_fourcc == PF_FOURCC("ATI1")) {
      |                                                         ^
modules/dds/texture_loader_dds.cpp:180:57: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
  180 |  } else if (format_flags & DDPF_FOURCC && format_fourcc == PF_FOURCC("ATI2")) {
      |                                                         ^
modules/dds/texture_loader_dds.cpp:183:57: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
  183 |  } else if (format_flags & DDPF_FOURCC && format_fourcc == PF_FOURCC("A2XY")) {
      |                                                         ^

thirdparty/assimp/include/assimp/material.inl: In member function 'aiReturn aiMaterial::Get(const char*, unsigned int, unsigned int, aiColor3D&) const':
thirdparty/assimp/include/assimp/material.inl:176:33: error: implicitly-declared 'aiColor3D& aiColor3D::operator=(const aiColor3D&)' is deprecated [-Werror=deprecated-copy]
  176 |     pOut = aiColor3D(c.r,c.g,c.b);

It had been done wrongly in #30185, but I missed it.

Godot core needs MD5/SHA256/AES/Base64 which used to be provided by
separate libraries.
Since we bundle mbedtls in most cases, and we can easily only include
the needed sources if we so desire, let's use it.

To simplify library changes in the future, and better isolate header
dependencies all functions have been wrapped around inside a class in
`core/math/crypto_base.h`.

If the mbedtls module is disabled, we only bundle the needed source
files independently of the `builtin_mbedtls` option.
If the module is enabled, the `builtin_mbedtls` option works as usual.

Also remove some unused headers from StreamPeerMbedTLS which were
causing build issues.

Add a Direction property to ParticlesMaterial

Add editor screenshot on control - f12.

Remove thread to prevent memory leak

Add XR mode selection to the Android export process.

Expand/collapse nodes recursively in scene tree dock

New contributor added to AUTHORS:
@aqnuep

Thanks to all contributors and donors for making Godot possible!

Add buttons to remove keys\items from dictionaries\arrays.