Group all tests of a test suite into a single test command invocation.
This reduces the number of invocations by `ctest` by an order of
magnitude.
Since rB56aa5b0d8c6b663, `bin/tests/blender_test` was run for every
individual test. Having over a 1000 tests made testing slower than
necessary. Individual tests can still be run if desired by invocation of
`bin/tests/blender_test --gtest_filter=suitename.testname`.
NOTE: For this commit to have an immediate effect, it may be necessary
to remove the `tests` and `Testing` directories and some CMake files
from your build directory and rebuild. Run `ctest -N` to see the list of
tests; there should be less than 200.
Reviewed By: sergey, LazyDodo, sebbas
Maniphest Tasks: T83222
Differential Revision: https://developer.blender.org/D9649
Add our own copy of the gtest discovery scripts from CMake a few reasons:
* Use the very latest version which supports PRE_TEST for Windows
* Fix usage of [] symbols in file paths that fail with the zsh shell
* Disable asan leak checker when discovering tests
This means Windows also no longer requires the very latest CMake 3.18.
