Make the tracing code and output more consistent and/or compact.

Also, restrict --trace-heap-broker to reports about missing data and
introduce a new flag --trace-heap-broker-verbose that prints everything.

Bug: v8:7790
Change-Id: I6e678fb97bf8631428594f77d8b5f0909ab2e281
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1559864Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60745}