Scons: fixed build for vanilla clang in mac os x

Fix some signals and non-debug branch for callable_mp

Add icons for some new variants

Changed default capsule axis to vertical

These bugs existed since those lines were added, so I assume that
their intended use is no longer relevant.

Was missed in #36393 because no `callable_mp()` calls were actually
compiled with `tools=no` in that PR.

Also work around GCC warning that also affects the
`call_with_variant_args_ret_helper` variant.

Store arrays inside of Variant as shared.

Arrays inside of Variant are unique and use reference counting.
When you assign a variant containing a packed array to another, or
when you call non const functions to arrays, this will work even
if the array is inside a dictionary, so they will from now pass
as reference.

The difference with regular variant arrays is that, once passed
to a function in the C++ API, they are no longer shared. This is
required for security and thread safety, as those arrays are
mainly used to pass data back and forth even between threads.

Fix: auto brace complete for quoted strings

Fix crash after closing a GDScript LSP session

SCons: Add GCC/Clang minimum version check

Co-authored-by: Hugo Locurcio <https://hugo.pro>

Prevent using GCC 8 as it does not properly support C++17's
guaranteed copy elision which we now need.
(Upstream bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86521)

Follow-up to #36457 and #36436.

Fix Breakpoint compare in new Debugger.

Only used to keep the hashmap, but clearly bogus.

Fix suspicious | and + operators

Added tween support for Rect2

Replace FALLTHROUGH macro by C++17 [[fallthrough]]

Fixes #34575

Add support for Vector2i, Rect2i and Vector3i to Variant

This attribute is now part of the standard we target so we no longer
need compiler-specific hacks.

Also enables -Wimplicit-fallthrough for Clang now that we can properly
support it. It's already on by default for GCC's -Wextra.

Fixes new warnings raised by Clang's -Wimplicit-fallthrough.

WARNING: Requires C++17 'guaranteed copy elision' to fix ambiguous
operator problems in Variant.

This was added for this commit (and future C++17 uses) in #36457.

Remove extra margin in the top of the debugger

SCons: Ensure that MSVC gets /std:c++17 in CCFLAGS

Travis: Use Xcode 11.3 for macOS/iOS

Xcode 10+ is needed for exhaustive C++17 support (gnu++17).

11.3 is the latest available version on Travis, and we don't have a
specific reason not to use it.

Follow-up to #36457.

We were running this logic too early, so `env.msvc` was not initialized
yet and MSVC used the same branch as GCC/Clang.

SCons: Bump required C++ standard to C++17

It's now available and allows us to have a better default environment,
with GCC 7.4.0 and Clang 7.

We now need GCC 7+ for C++17 support so it's more efficient to upgrade
the image than to install it on Ubuntu 16.04 (xenial).

Also fixes a couple -Wdeprecated-declarations warnings on macOS now
that we build against macOS 10.12.

As per #36436, we now need C++17's guaranteed copy elision feature to
solve ambiguities in Variant.

Core developers discussed the idea to move from C++14 to C++17 as our
minimum required C++ standard, and all agreed. Note that this doesn't
mean that Godot is going to be written in "modern C++", but we'll use
modern features where they make sense to simplify our "C with classes"
codebase. Apart from new code written recently, most of the codebase
still has to be ported to use newer features where relevant.

Proper support for C++17 means that we need recent compiler versions:

 - GCC 7+
 - Clang 6+
 - VS 2017 15.7+

Additionally, C++17's `std::shared_mutex` (conditionally used by
`vk_mem_alloc.h` when C++17 support is enabled) is only available in
macOS 10.12+, so we increase our minimum supported version.

Fix visuals of the new debugger editor

Vulkan: Work around false positive on 64-bit Linux w/ 32-bit ICDs