This change adds control flow to ensure that an OSR method for a patchpoint
nested in try regions enters those regions try from the first block of each
try rather than mid-try.

This lets these OSR methods conform to the data flow expectations that the
only way control flow can enter a try is via its first block.

See dotnet#33658 for more details on the approach taken here.

Fixes dotnet#35687.

…PostImporter