Perf: Use [GeneratedRegex] where possible

[N-Olbert]

XmlDocumentationProvider contains two frequently used regular expressions that are interpreted rather than compiled. Noticeable performance improvements from #8794 are simply from converting them to [GeneratedRegex]. Since 16 is about to become an RC soon, I assume that XmlDocumentationProvider will remain mostly unchanged, which is why I pulled this change out separately.

A quick search also revealed other places where interpreted regexes - or, in comparison, less optimal regexes using RegexOptions.Compiled - were used. I converted those as well and activated SYSLIB1045 as a warning.

One might argue whether SYSLIB1045 should be active for test projects, but given that Assert.Matches(string pattern, ...) exists, I think it is reasonable.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (d2626ce) to head (c31d0ba).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@     Coverage Diff      @@
##   main   #9322   +/-   ##
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