This adds the option to output statistics about the embedded blob.

On x64 release, the output is currently:

Total size:                         724064
Metadata size:                      6832
Instruction size:                   703427
Padding:                            13805
Embedded builtin count:             852
Instruction size (50th percentile): 222
Instruction size (75th percentile): 749
Instruction size (90th percentile): 1871
Instruction size (99th percentile): 9171

Total size is added to our Memory benchmark.

Drive-by: Fix startup / context regexps for Memory benchmark.

Bug: v8:6666, v8:7898
Change-Id: I90d4458877939d3b48593bd9dd3a33971fe78c44
Reviewed-on: https://chromium-review.googlesource.com/1126104
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54256}