Async functions were not correctly fixed up for code coverage, which
caused an additional uncovered range to be reported between a return
statement and the closing bracket.

This CL adds code that detects such ranges, and removes them, similarly
to how the ranges are removed for normal functions. The removal process
is different, because the parser rewrites async functions to contain a
try-catch handling promise rejection.

Change-Id: I73b08d64be74d26c32f2f9652d027430d4671251

Bug: chromium:981313, v8:8381
Change-Id: I82a7f0c54d3a48609ef5255a7659d9557e163566
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1782837Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63561}