Tracks background compilation of Ignition in a separate bucket from main thread
compilation. Also add some more compilation buckets for functions which can take a
significant proportion of compilation.

BUG=v8:5203,v8:5215

Review-Url: https://codereview.chromium.org/2577263002
Cr-Original-Commit-Position: refs/heads/master@{#42026}
Committed: https://chromium.googlesource.com/v8/v8/+/b0e9116d59326a4f9a4f4691b61a510e342338c9
Review-Url: https://codereview.chromium.org/2577263002
Cr-Commit-Position: refs/heads/master@{#42042}