Add CMake package config file

This change enables automatic detection and consumption of Mbed TLS
library targets from within other CMake projects. By generating an
`MbedTLSConfig.cmake` file, consuming projects receive a more complete
view of these targets, allowing them to be used as dependencies which
properly inherit the transitive dependencies of the libraries.

This is fairly fragile, as it seems Mbed TLS's libraries do not appear
to properly model their dependencies on other targets, including
third-party dependencies. It is, however, sufficient for building and
linking the compiled Mbed TLS libraries when there are no third-party
dependencies involved. Further work is needed for more complex
use-cases, but this will likely meet the needs of most projects.

Resolves #298. Probably useful for #2857.

Signed-off-by: Chris Kay <chris.kay@arm.com>

tests/scripts/all.sh

@@ -273,7 +273,7 @@ cleanup()
            -iname CMakeFiles -exec rm -rf {} \+ -o \
            \( -iname cmake_install.cmake -o \
               -iname CTestTestfile.cmake -o \
-              -iname CMakeCache.txt \) -exec rm {} \+
+              -iname CMakeCache.txt \) -exec rm -f {} \+
     # Recover files overwritten by in-tree CMake builds
     rm -f include/Makefile include/mbedtls/Makefile programs/*/Makefile
     git update-index --no-skip-worktree Makefile library/Makefile programs/Makefile tests/Makefile programs/fuzz/Makefile
@@ -284,6 +284,16 @@ cleanup()
     rm -f programs/test/cmake_subproject/Makefile
     rm -f programs/test/cmake_subproject/cmake_subproject
 
+    # Remove any artifacts from the component_test_cmake_as_package test.
+    rm -rf programs/test/cmake_package/build
+    rm -f programs/test/cmake_package/Makefile
+    rm -f programs/test/cmake_package/cmake_package
+
+    # Remove any artifacts from the component_test_cmake_as_installed_package test.
+    rm -rf programs/test/cmake_package_install/build
+    rm -f programs/test/cmake_package_install/Makefile
+    rm -f programs/test/cmake_package_install/cmake_package_install
+
     if [ -f "$CONFIG_BAK" ]; then
         mv "$CONFIG_BAK" "$CONFIG_H"
     fi
@@ -2609,6 +2619,32 @@ component_test_cmake_as_subdirectory () {
     unset MBEDTLS_ROOT_DIR
 }
 
+component_test_cmake_as_package () {
+    msg "build: cmake 'as-package' build"
+    MBEDTLS_ROOT_DIR="$PWD"
+
+    cd programs/test/cmake_package
+    cmake .
+    make
+    if_build_succeeded ./cmake_package
+
+    cd "$MBEDTLS_ROOT_DIR"
+    unset MBEDTLS_ROOT_DIR
+}
+
+component_test_cmake_as_package_install () {
+    msg "build: cmake 'as-installed-package' build"
+    MBEDTLS_ROOT_DIR="$PWD"
+
+    cd programs/test/cmake_package_install
+    cmake .
+    make
+    if_build_succeeded ./cmake_package_install
+
+    cd "$MBEDTLS_ROOT_DIR"
+    unset MBEDTLS_ROOT_DIR
+}
+
 component_test_zeroize () {
     # Test that the function mbedtls_platform_zeroize() is not optimized away by
     # different combinations of compilers and optimization flags by using an