[bazel] re-org bazel logs per fx-build/invocation

Organize bazel logs per fx-build, per invocation.

log structure:
out/_build_logs/OUTDIR_BASENAME/build.$date.XXXXXXXX/bazel_logs/invocation-$date--$id

wrapper.bazel.sh: dynamically set per-invocation log dir under
$FX_BUILD_LOGDIR as per above log structure.
Removed log-rotation, now that we capture everything.

workspace_utils.py: no longer place logs_dir under top_dir.

template.bazelrc: moved log flags to wrapper.bazel.sh

template.bazel.sh.config: removed log dir, now dynamic in
wrapper.bazel.sh.

'fx report-last-build' automatically includes everything under
the per-fx-build _build_logs dir.

bazel->ResultStore should still upload the relocated logs as invocation
artifacts using their basename (unchanged).

Fixed: 490517609
Change-Id: Id5313f2702dd12d3ce237027d62fd4891e1bdd9e
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1531621
Reviewed-by: Jay Zhuang <jayzhuang@google.com>
Commit-Queue: Jay Zhuang <jayzhuang@google.com>