We still see occasions of "WebAssembly Instantiation: Out of memory:
wasm memory", e.g. on the N5X arm64 bot.

We already have a retry-loop around the {ReserveAddressSpace} call, so
this error can only happen if {AllocatePages} fails.
I cannot easily reproduce, so I will land this CL and hope that it
fixes the flake.

We might eventually replace all these gc-then-retry loops by a better
mechanism which knows about process-wide allocations. Currently,
{AllocatePages} is isolate-independent, and only calls
{Platform::OnCriticalMemoryPressure}, but this call does nothing on the
default platform. So trigger a GC on the current isolate instead.

R=mlippautz@chromium.org

Bug: chromium:883639, v8:7872, v8:8158
Change-Id: Ib4e4a4a5f6b598d5832c327b1fc83ccb3bada9bc
Reviewed-on: https://chromium-review.googlesource.com/1226886Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55955}