[interp] Simplify the main interpreter loop code to speed up compilation. (mono/mono...

[interp] Simplify the main interpreter loop code to speed up compilation. (mono/mono#15889)

* [interp] Simplify the control flow in the main loop to speed up compilation of interp.c.

Get rid of the handle_finally and main_loop labels.

* [interp] Move some rarely used locals to InterpFrame to speed up compilation and to increase the chance that the other locals end up in registers.

* Add macros for throwing exceptions to shorten the code a bit.

* Fix a previous change.

Commit migrated from https://github.com/mono/mono/commit/f8fd60b5c088753a4a0ccb79483ebae73489e7a2