Add submits after flushes in ProgramsTest.
Add submits after flushes in ProgramsTest.

This looks to be the culprit behind the failing/flaky metal bots. Not
sure what the direct cause is because it was different tests that were
failing and I would have thought we'd eventually submit at the end of
ProgramsTest when tearing things down. Maybe we just created such a
backlog of work submitted to the actual GPU that the GPU got put into
a bad state?

Bug: skia:10118
Change-Id: I318428e228e08fbcaaa12b23ad2869ecc35cc786
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/283136
Reviewed-by: Brian Salomon <61fabaaf0876044aeedfd8e351e485c028d69e7b@google.com>
Commit-Queue: Greg Daniel <39df0a804564ccb6cf75f18db79653821f37c1c5@google.com>

google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia