Simplify JIT-EE interface modification

Despite the fact it was partially automated in the past it's still quite exhausting to add new APIs, I propose to address at least these issues:

• Autogenerate corinfo.h (e.g. introduce corinfo_generated.h) part from ThunkInput.txt - we can move comments to ThunkInput.txt
• Autogenerate superpmi-shim-simple\icorjitinfo.cpp
• Autogenerate superpmi-shim-collector\icorjitinfo.cpp
• Append _generated.h to all auto-generated files (currently there are still like 5 or 6 auto-generated files without them - it helps to ignore them when adding a new API) - https://github.com/dotnet/runtime/pull/77083
• gen.bat emits two new-lines in the end of CorInfoBase.cs breaking compilation - https://github.com/dotnet/runtime/pull/77083
• Ensure gen.bat is no-op on unchanged codebase on CI

category:cq theme:jit-ee-interface skill-level:beginner cost:small impact:small