Port 2.0: Prep tests for CoreCLR/CoreRT [Serializable] cleanup (#20035)

[morganbr]

2.0 port of #20035 Fixes tests that depend on types in System.Private.CoreLib being serializable that won't be serializable soon.

Fixes https://github.com/dotnet/corefx/issues/20041.

[morganbr]

CC @danmosemsft @tarekgh @dotnet/corert-contrib

[tarekgh]

LGTM. Thanks @morganbr

[danmoseley]

Let's gather all changes and talk to shiproom before merging.

[tarekgh]

Let's gather all changes and talk to shiproom before merging.

Is this will be done through the email or there is scheduled meeting for it?

[danmoseley]

Is this will be done through the email or there is scheduled meeting for it?

We are doing shiproom by email this week. We may end up going to shiproom physically on Thursday given the size of the change. We will have to explain that we will need to synchronize changes back and forth between coreclr and corefx which may take a couple days.

[tarekgh]

@danmosemsft any update regarding the shiproom?

[danmoseley]

@tarekgh I have a conflict, but I'll send an update mail beforehand. Clearly we can't take it today.

[danmoseley]

@morganbr I guess this is defunct?

[morganbr]

@danmosemsft yep. I'll close it out.