UnoptimizedCompileFlags defines the input flags shared between parse and
compile (currently parse-only). It is set initially with some values, and
is immutable after being passed to ParseInfo (ParseInfo still has getters
for the fields, but no setters).

Since a few of the existing flags were output flags, ParseInfo now has a
new output_flags field, which will eventually migrate to a ParseOutputs
structure.

Bug: v8:10314
Change-Id: If3890a5fad883bca80a97bf9dfe44d91797dc286
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2096580
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66782}