This CL introduces, and turns on by default, compression for snapshots.
The compression is handled in SnapshotCompression, which is a new static
helper class for producing/consuming compressed SnapshotData.

To turn off snapshot compression (accomplished by removing calls of
Compress/Decompress) set the GN arg:
v8_disable_snapshot_compression = true


Bug: chromium:833361
Change-Id: If8abc3662e8473fbd0c94e443946fbea804a305e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1846066
Commit-Queue: Sam Maier <smaier@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66230}

adler32 is strictly faster than the old checksum - see this doc:
https://docs.google.com/document/d/1fFhuShavlUwf0FqTc-6L3XLYbAVe0DhpmHSv4oenZL8/edit?pli=1#heading=h.ojvfq6akbz5f

adler32 also no longer requires alignment to be maintained.

Bug: chromium:833361
Change-Id: I3dbfa699b712aa908c87e6f8261756a4a1209df4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1925562
Commit-Queue: Sam Maier <smaier@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65160}

R=jochen@chromium.org

Review URL: https://codereview.chromium.org/1041743002

Cr-Commit-Position: refs/heads/master@{#27501}