Enable EnC of methods containing switch expressions

[tmat]

Switch expressions EnC is disabled in 16.3 due to bugs:

• Compiler emits incorrect EnC closure data to PDB for nested switch expressions #37232
• Expression bodied method whose expression is a switch expression is missing debug info #37261
• Compiler shouldn't emit hidden sequence points on display class creation instruction in expression context #37237
• Duplicate locals are emitted for switch expression arms #50301
• Closure info in PDB is wrong for nested switch expressions #50321

We need to revisit how closures are emitted for lifted variables declared in the switch expression.

[davidwengier]

Currently blocked by #50301 and #50321