Look into supporting CMake's generic test discovery

**Description**
Since 4.4, CMake has support for generic test discovery from a binary. It supports most features from our current discovery mechanism (except for writing through a file), but relies on regex + plain stdout to exchange the information.

**Additional context**
https://cmake.org/cmake/help/latest/command/discover_tests.html#command:discover_tests

Start with CMake's discover_tests documentation linked in the issue, then locate Catch2's current CMake test-discovery mechanism. Compare the supported features and identify the entry points needed for generic binary discovery using regex and stdout. Done means Catch2 supports the requested generic discovery behavior while retaining the documented limitation around writing through a file.

Written by the indexing model from the issue text.