Revert "[ir][fuzz] Add missing validation logging"

This reverts commit bb580872591b316008a7328e48e30001347fca0c.

Reason for revert: unintentionally disables validation on many fuzzing bots (ValidateAndDumpIfNeeded only validates if a build-time flag is set)

Original change's description:
> [ir][fuzz] Add missing validation logging
>
> This adds logging to the pre and post run stages of the fuzzer when
> the validator is asked to dump shader state. This makes it very clear
> what state the shader was in before and after running the pass, as
> well as clears up if failures occur on the last transform being run,
> or on the final pass validation.
>
> With #define TINT_DUMP_IR_WHEN_VALIDATING 1 this will add
> =========================================================
> == IR dump before start:
> =========================================================
> <shader ir>
>
> and
>
> =========================================================
> == IR dump before exit:
> =========================================================
> <shader ir>
>
> to the begin/end of a pass's log, matching the style of the logging
> that appears before each transform runs.
>
> Fixes: 483966080
> Change-Id: I174715fcaf1733fefb4f96a00aa6e8c7570c56e2
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/290595
> Commit-Queue: dan sinclair <dsinclair@chromium.org>
> Reviewed-by: James Price <jrprice@google.com>
> Reviewed-by: dan sinclair <dsinclair@chromium.org>
> Commit-Queue: Ryan Harrison <rharrison@chromium.org>
> Auto-Submit: Ryan Harrison <rharrison@chromium.org>

TBR=rharrison@chromium.org,dsinclair@chromium.org,jrprice@google.com,dawn-scoped@luci-project-accounts.iam.gserviceaccount.com

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: Ia58d8463bb378378300677f9e5c3d00f96b4665b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/290875
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: James Price <jrprice@google.com>