The latter is better because it takes field type into account when
decompressing field value.

Drive-by: use [DECL_]ACCESSOR macros for some fields.

Bug: v8:9353
Change-Id: I3d7f07d11b1e379e3e6cf0310d836af6b48c1338
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1680539
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62444}