Previously, we finalize all compile jobs at once. This keeps the zone memory
in every compile job alive until the end. This contributes to a high peak
memory when many functions are compiled eagerly, for example when producing
cache data for the ServiceWorker cache.

Memory tracked by the AccountingAllocator in bytes, prior to this change in
the test case:
peak memory after init:              8192
peak memory after lazy compile:     41200
peak memory after lazy compile:     41200
peak memory after eager compile:   164256

With this change, if we are compiling on the main thread, we finalize every
compile job as soon as it is done and dispose the compile job and its zone
memory.

After this change:
peak memory after init:              8192
peak memory after lazy compile:     41200
peak memory after lazy compile:     41200
peak memory after eager compile:    41376

R=leszeks@chromium.org, rmcilroy@chromium.org

Bug: chromium:901329
Change-Id: Iae0c89396c89692c4ecdeec3970d3c62031d2bce
Reviewed-on: https://chromium-review.googlesource.com/c/1322949
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57340}