When collecting JS block coverage, we track block execution counts on
so-called CoverageInfo objects. Generated bytecode and native code
contains inlined snippets of code to increment the appropriate
counters.

These used to be implemented as calls to the IncBlockCounter runtime
function. Each call incurred the entire CEntry overhead.

This CL reduces that overhead by moving logic over into a new
IncBlockCounter TFS builtin. The builtin is called directly from
bytecode, and lowered to the same builtin call for optimized code.

Drive-by: Tweak CoverageInfo layout to generate faster code.

Tbr: jarin@chromium.org
Bug: v8:9149, v8:6000
Change-Id: I2d7cb0db649edf7c56b5ef5a4683d27b1c34605c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1571420Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60981}