R2RDump - Test infrastructure (dotnet/coreclr#18745)

R2RDump - Test infrastructure (dotnet/coreclr#18745)

* Test infrastructure for R2RDump, compare xml and output diff

* Add R2RDumpTest to build-tests

* Fix errors causing tests to fail

* Create XUnitWrapper for R2RDumpTest

* Generate readytorun binaries from source code, copy expected xml output files to executable's directory

* Test R2RDump through commandline instead of calling R2RDump functions

* Fix errors

* Prevent duplicate xml tags

* Read test xml from string instead of file

* Fix test bugs

* Call dotnet r2rdump from msbuild

* Fix errors

* Use right slash for paths in bash

* Use different expected xml for different architectures

* R2RDumpTests for non-Windows

* Add more test cases

* Fix errors

* Supress warnings, avoid error when parsing x86 images

* Add license headers

Commit migrated from https://github.com/dotnet/coreclr/commit/eb622bef3851f8858db8d365454f1345e270dcd8