Support @clientName and @encodedName in dotnet CodeGen

[lirenhe]

As encodedName is introduced in 0.52 of TypeSpec.

model Widget {
  @key id: string;

  @encodedName("application/json", "WidgetWeight")
  weight: int32;
  
  color: "red" | "blue";
  @added(Versions.v2) name: string;
}

And @clientName is introduced in this PR https://github.com/Azure/typespec-azure/pull/127/files.

Please support them in the CodeGen.

[timotheeguerin]

Tcgc abstract that away from you and should have just worked. Call getLibraryName

[lirenhe]

The adoption of TCGC is still in progress. #4185
We may implement that separately to unblock customer and then move to using TCGC. cc @m-nash

[timotheeguerin]

any progress on this? are we still blocked on doing this migration?

[pshao25]

any progress on this? are we still blocked on doing this migration?

I'm blocked by #4212