Use code generated or compiled regular expressions where possible

[SukharevAndrey]

This PR replaces all regular expression usages in the project with source generated or at least dynamically compiled ones. It should increase performance a bit, especially in code generator which is now using source generators, isn't it? Also projects using Orleans will have more room for their regexps' cache because global Regex cache's size is quite small (15) and Orleans will not use it now.

As it is my first contribution to Orleans, I still have questions:

• I have doubts about using source generated regexps due to the fact that classes containing regexps need to be made partial. Is this OK? Should I change that usages to ordinary regexps with Compiled option?
• I have some more low-hanging fruits in mind to fix. Should I create an issue for that (including this PR)?

I'm planning to do more meaningful contributions (such as analyzers) so any feedback is appreciated. Thanks.

Microsoft Reviewers: Open in CodeFlow

[dnfadmin]

All CLA requirements met.