Regex fixes for substring parsing.
Miscellaneous changes per review
[runtime] Don't assert when loading a generic methodspec with 0 arity (xambug #19097).
[jit] Emit OP_FMOVE instead of OP_MOVE for r4 arguments in hard float mode on arm.
[profiler] Increase the number of maximum and default frames in backtraces.
Test Decimal.ToString after rounding with trailing zeros.
Decimal.Round output no longer keeps trailing zeros.
Add test for Regex RTL substring matching.
[jit] Use the mono_mutex types/functions of CriticalSection's.
[runtime] Use the mono_mutex types/functions instead of CriticalSection's.
[runtime] Remove unused critical-sections files.
Fix the build.
Added MonoString<->UTF-32 conversion helper functions.
[mcs] switch statement with constant block at first label. Fixes #21805
Merge pull request #1180 from akoeplinger/no-net40-in-make-check

Don't run net_4_0 tests during "make check"
Merge pull request #1193 from esdrubal/decimal-round

Decimal.Round trailing zeros
Merge pull request #1168 from esdrubal/iriparsing

IriParsing
[System] Fix parsing of URI schemes with digits

Initializing an Uri previously throwed an exception when the URI scheme contained a digit (e.g. net.p2p).
The loop was missing a digit check, similar to https://github.com/mono/mono/blob/1f1dc988ad7b165603a1175bf0a92156c4372c43/mcs/class/System/System/Uri.cs#L767
Merge pull request #1195 from akoeplinger/fix-uri-with-digits

[System] Fix parsing of URI schemes with digits
Correct code review comments on test