This reverts commit d8f8a7e2.

Reason for revert: Breaks code_serializer variant - https://cr-buildbucket.appspot.com/build/8874070652992164976

Original change's description:
> Reland "[flags] warn about contradictory flags"
> 
> This is a reland of b8f91666
> Difference to previous CL: Additional functionality to specify
> incompatible flags based on GN variables and extra-flags, used
> to fix the issues that came up on the waterfall.
> 
> This also changes the rules regarding repeated flags: While
> explicitly repeated flags are allowed for boolean values as long
> as they are identical, repeated flags or explicit flags in the
> presence of an active implication are disallowed for non-boolean
> flags. The latter simplifies specifying conflict rules in
> variants.py. Otherwise a rule like
> 
> INCOMPATIBLE_FLAGS_PER_EXTRA_FLAG = {
>   "--gc-interval=*": ["--gc-interval=*"],
> }
> 
> wouldn't work because specifying the same GC interval twice
> wouldn't actually count as a conflict. This was an issue with
> test/mjsunit/wasm/gc-buffer.js, which specifies
> --gc-interval=500 exactly like the extra flag by the stress bot.
> 
> Also, this now expands contradictory flags checking to d8 flags
> for consistency.
> 
> Original change's description:
> > [flags] warn about contradictory flags
> >
> > Design Doc: https://docs.google.com/document/d/1lkvu8crkK7Ei39qjkPCFijpNyxWXsOktG9GB-7K34jM/
> >
> > Bug: v8:10577
> > Change-Id: Ib9cfdffa401c48c895bf31caed5ee03545beddab
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2154792
> > Reviewed-by: Clemens Backes <clemensb@chromium.org>
> > Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> > Reviewed-by: Georg Neis <neis@chromium.org>
> > Reviewed-by: Tamer Tas <tmrts@chromium.org>
> > Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#68168}
> 
> Bug: v8:10577
> Change-Id: I268e590ee18a535b13dee14eeb15ddd0a9ee8341
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2235115
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Tamer Tas <tmrts@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#68989}

TBR=machenbach@chromium.org,neis@chromium.org,clemensb@chromium.org,tebbi@chromium.org,tmrts@chromium.org

Change-Id: I7969065b0edbc463a94e530485bc2ab623d77b62
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10577
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2312782Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68992}