Reenable some disabled warnings in CoreCLR

[ivdiazsa]

This is a followup to PR #33902, which has been reviewed and approved. The reason for this new PR, is that Azure Pipelines tests got stuck and the solution was to get the latest changes. When rebasing the branch with master, all those commits and changes were added to the PR, thus rendering it entirely uninformative, and therefore useless for historic study and statistics.

Fixes #33743.

Added some necessary casts and fixed string formats to comply with warnings 4302, 4311, 4312, and 4477 in CoreCLR. Having these warnings back on will help improve code quality and reduce potential scenarios where unpredicted behavior might cause further issues.

[trylek]

LGTM, thanks Ivan for your tenacity in fighting GitHub quirks! Please just make sure to use a squash merge to spare us the details of your fight ;-).

[janvorli]

There are still some warnings that cause build break in the GCC build:

2020-04-07T23:09:31.6969516Z In file included from /__w/1/s/src/coreclr/src/jit/codegeninterface.h:27:0,
2020-04-07T23:09:31.6971238Z                  from /__w/1/s/src/coreclr/src/jit/compiler.h:52,
2020-04-07T23:09:31.6972337Z                  from /__w/1/s/src/coreclr/src/jit/jit.h:800,
2020-04-07T23:09:31.6977378Z                  from /__w/1/s/src/coreclr/src/jit/jitpch.h:19,
2020-04-07T23:09:31.6978600Z                  from /__w/1/s/src/coreclr/src/jit/alloc.cpp:5:
2020-04-07T23:09:31.7071934Z /__w/1/s/src/coreclr/src/jit/emit.h:522:51: warning: 'emitter::emitAddrMode::amBaseReg' is too small to hold all values of 'regNumber {aka enum _regNumber_enum}'
2020-04-07T23:09:31.7073513Z          regNumber       amBaseReg : REGNUM_BITS + 1;
2020-04-07T23:09:31.7074589Z                                                    ^

[ivdiazsa]

There are still some warnings that cause build break in the GCC build:
2020-04-07T23:09:31.6969516Z In file included from /__w/1/s/src/coreclr/src/jit/codegeninterface.h:27:0,
2020-04-07T23:09:31.6971238Z from /__w/1/s/src/coreclr/src/jit/compiler.h:52,
2020-04-07T23:09:31.6972337Z from /__w/1/s/src/coreclr/src/jit/jit.h:800,
2020-04-07T23:09:31.6977378Z from /__w/1/s/src/coreclr/src/jit/jitpch.h:19,
2020-04-07T23:09:31.6978600Z from /__w/1/s/src/coreclr/src/jit/alloc.cpp:5:
2020-04-07T23:09:31.7071934Z /__w/1/s/src/coreclr/src/jit/emit.h:522:51: warning: 'emitter::emitAddrMode::amBaseReg' is too small to hold all values of 'regNumber {aka enum _regNumber_enum}'
2020-04-07T23:09:31.7073513Z regNumber amBaseReg : REGNUM_BITS + 1;
2020-04-07T23:09:31.7074589Z ^

Those are new! Let me take a look and fix them. Thanks for pointing them out Jan.