* Fix EnC debug information emitted for patterns

Update calculation of syntax offset to account for a new case when a node (a switch expression) that is associated with a variable, closure or lambda may share start offset with other node of the same kind (`expr switch { … } switch { … }`). Use the offset of the `switch` keyword instead of the starting offset of the expression to disambiguate.

Assign ordinals to variables synthesized for storing pattern values across cases. This is required to support complex patterns since we can no longer rely on the type of these variables to be distinct. This will require follow up in the IDE to disallow updating/adding/reordering the case clauses of switch expression which there an active statement is present within the switch statement. If the cases are unmodified the compiler guarantees that the order in which the synthesized variables are generated remains the same, so we can map the variables using their ordinal.

Mark all variables synthesized during lowering of switch expression as short-lived. Their lifespan is limited to the switch expression, which does not include a sequence point.

Disallow editing methods that contain switch expression. This is necessary until bugs https://github.com/dotnet/roslyn/issues/37232, https://github.com/dotnet/roslyn/issues/37237 are fixed.

* Feedback

* Update tests