Dictation: Add C++ tests for remaining Pumpkin commands

This change adds C++ tests for the remaining commands supported by
Pumpkin. These tests closely mirror their DictationCommandsTest
equivalents. The big difference is that we use a different utterance
to invoke the command; these utterances do not exist as regular
expressions, thus we know that the speech parsing is done by
Pumpkin.

AX-Relnotes: N/A
Bug: 1258190
Change-Id: I084405fbb0b9fdef7ff7b791635d3fd513e72e2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3950554


Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1061581}