Add WGSL support for break, continue, and nop statements.

These statements are very straightforward and don't need special
handling. This unlocks a handful of additional tests.

Change-Id: I94fb48979430dd67b483afd0cf2200ec55428cfa
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/707420
Reviewed-by: Arman Uguray <armansito@google.com>
Commit-Queue: Arman Uguray <armansito@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
10 files changed