Reset assignedInterval during verifyFinalAllocation

[kunalspathak]

My latest changes to EH Var for single defs exposed 2 more issues where we were not resetting the assignedInterval of a assigned reg:

1. For RefTypeDef, if an interval doesn't get assigned to a new register, then reset the assignedInterval of the regRecord that is currently assigned to that interval.
2. Again, for RefTypeDef, if an interval got assigned to a different register than the original assignReg of that interval and if that refposition is spilled immediately, then reset the assignedInterval of such regRecord.

Both of the above scenarios were exposed because they were EH Vars. In verifyFinalAllocation(), there are multiple places where we check for RefTypeDef and take action and I looked into consolidating all the logic at single place, but I was not sure if it will regress in the way we print the "Final allocation table". Hence, to honor the time, I went ahead and did the spot fixing of these 2 scenarios, but in future, will try to refactor various scenarios.

Fixes errors:

• https://dev.azure.com/dnceng/public/_build/results?buildId=1024357&view=ms.vss-test-web.build-test-results-tab
• https://dev.azure.com/dnceng/public/_build/results?buildId=1021926&view=ms.vss-test-web.build-test-results-tab

[kunalspathak]

@dotnet/jit-contrib

[benaadams]

Code formatting issue on Linux?

[kunalspathak]

Code formatting issue on Linux?

Oh yes, fixed.