Cleanup: remove empty try's

[danmoseley]

We have about 20 instances of try { }

See https://github.com/dotnet/coreclr/issues/8924.

The PR dotnet/coreclr#8949 makes sure they are not represented in generated code so this is just minor code cleanup.

[benaadams]

Can they be removed in corefx? e.g. can corefx be used over a runtime other than coreclr that has ThreadAbort?

[danmoseley]

I was assuming CoreRT/PN (and CoreCLR) do not, and those are the only contexts for CoreRT. @jkotas can you confirm? I don't think we've been maintaining these or considering thread aborts when working on CoreFX.

[jkotas]

They can be removed in netcoreapp-specific parts.

We may want to preserve them in parts that target netstandard because of those parts can run on runtimes that have thread abort. But I would not go out of our way to explicitly harden these parts for threadabort (it is super expensive to do it right).