Add test for TLS_VERIFY to CMake itself

!8184 (merged) re-enabled TLS 1.3 on Windows. However, I don't see any TLS_VERIFY online tests under CMake's own Tests/ directory. The problem symptoms driving this series of PRs were discovered by me in CMake 3.25.0-rc4, which is rather late in the RC cycle.

I would like to add an online CMake self-test--perhaps disabled by default--that checks file(DOWNLOAD ... TLS_VERIFY true) on CMake's nightly tests to help avoid a future problem like this slipping through.

For example, gitlab.kitware.com is TLS 1.3 enabled