Modernise Existing CMakeLists.txt

- Added to .gitignore CMakeUserPresets.json

### Configuration:
- Changed python command to use single quotes to make build output log more legible.
- Added GODOT_DEV_BUILD to allow differentiation of debug or Release builds.
- Added find logic for macos Cocoa library

### godot-cpp Changes
- godot-cpp-test is changed to be incorporated into the cmake build as a target.
- Duplicated godot-cpp target into [template_release, template_debug, editor]
- Created {platform}.cmake files mirroring the style of the SCons build.

CMake has a feature called generator expressions for its configuration variables that are evaluated at build time. This allows multi-configuration build systems to properly evaulate options. for msvc, xcode and nijna multi-config.

- Moved configuration options to generator expressions with the notable exclusion of OSX_ARCHITECTURES.
- Remove CMAKE_BUILD_TYPE from msvc CI target as Multi-Config generators ignore it

### godot-cpp-test Changes
- Removed majority of the cmake code, now that the godot-cpp project is setup, the majority of the flags will be propagated as transient dependencies
- Marked with EXCLUDE_FROM_ALL so that it isn't built as part of the 'all' target
- Updated ci to build the godot-cpp-test target from the root directory using cmake
- Tests passing for Windows, Linux, and Macos builds.

### Documentation
Updated with new information
Added Emscripten example
Added Android example

.github/workflows/ci.yml

@@ -207,30 +207,6 @@ jobs:
           path: ${{ matrix.artifact-path }}
           if-no-files-found: error
 
-  linux-cmake:
-    name: 🐧 Build (Linux, GCC, CMake)
-    runs-on: ubuntu-22.04
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          submodules: recursive
-
-      - name: Install dependencies
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -qqq build-essential pkg-config cmake
-
-      - name: Build godot-cpp
-        run: |
-          cmake -DCMAKE_BUILD_TYPE=Release .
-          make -j $(nproc) VERBOSE=1
-
-      - name: Build test GDExtension library
-        run: |
-          cd test && cmake -DCMAKE_BUILD_TYPE=Release -DGODOT_HEADERS_PATH="../godot-headers" -DCPP_BINDINGS_PATH=".." .
-          make -j $(nproc) VERBOSE=1
-
   linux-cmake-ninja:
     name: 🐧 Build (Linux, GCC, CMake Ninja)
     runs-on: ubuntu-22.04
@@ -245,15 +221,12 @@ jobs:
           sudo apt-get update -qq
           sudo apt-get install -qqq build-essential pkg-config cmake ninja-build
 
-      - name: Build godot-cpp
-        run: |
-          cmake -DCMAKE_BUILD_TYPE=Release -GNinja .
-          cmake --build . -j $(nproc) --verbose
-
       - name: Build test GDExtension library
         run: |
-          cd test && cmake -DCMAKE_BUILD_TYPE=Release -DGODOT_HEADERS_PATH="../godot-headers" -DCPP_BINDINGS_PATH=".." -GNinja .
-          cmake --build . -j $(nproc) --verbose
+          mkdir cmake-build
+          cd cmake-build
+          cmake ../ -DTEST_TARGET=template_release
+          cmake --build . --verbose -j $(nproc) -t godot-cpp-test --config Release
 
   windows-msvc-cmake:
     name: 🏁 Build (Windows, MSVC, CMake)
@@ -264,12 +237,9 @@ jobs:
         with:
           submodules: recursive
 
-      - name: Build godot-cpp
-        run: |
-          cmake -DCMAKE_BUILD_TYPE=Release -G"Visual Studio 16 2019" .
-          cmake --build . --verbose --config Release
-
       - name: Build test GDExtension library
         run: |
-          cd test && cmake -DCMAKE_BUILD_TYPE=Release -DGODOT_HEADERS_PATH="../godot-headers" -DCPP_BINDINGS_PATH=".." -G"Visual Studio 16 2019" .
-          cmake --build . --verbose --config Release
+          mkdir cmake-build
+          cd cmake-build
+          cmake ../ -DTEST_TARGET=template_release
+          cmake --build . --verbose -t godot-cpp-test --config Release