This reverts commit ca931562.

Reason for revert: tsan:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20TSAN/builds/16007

Original change's description:
> [wasm] Allow the initialization of a single compilation unit
> 
> This CL adds a new function {InitializeCompilationUnit} to initialize
> a single compilation unit and not just all compilation units at once.
> This is necessary for streaming compilation eventually. This also
> required some refactoring on how the working queue for compilation units
> works. Previously the synchronization was done with an atomic counter,
> now it is done with a lock. Note that the code to finish compilation
> of a module still only works if the working queue gets only empty when
> all work is done. I plan to change this in a different CL.
> 
> Since the code would not be tested without streaming compilation, I added
> an experimental flag and a test to test the new code.
> 
> R=​clemensh@chromium.org, mtrofin@chromium.org
> 
> Change-Id: I839c04fd78d1ea8e1db202f2cbed41c4c2cf4f28
> Reviewed-on: https://chromium-review.googlesource.com/550096
> Commit-Queue: Andreas Haas <ahaas@chromium.org>
> Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
> Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#46348}

TBR=mtrofin@chromium.org,ahaas@chromium.org,clemensh@chromium.org

Change-Id: Ied6532f05463c0b78c8b8f5307d44640bcca8316
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/558224Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46350}