During Module::Reset(), the module is in an unstable state between the
change to SourceTextModule::code and Module::status.  Any reentrancy
between these points is problematic because the normal invariants about
the value of SourceTextModule::code in relation to Module::status do not
hold.

An allocation of the exports hash table in the middle of Module::Reset()
was causing reentrancy during this problematic time.  This change fixes
the issue by moving the allocation earlier in Reset() before any fields
are modified.

Bug: v8:9522
Change-Id: Ia941af60a0b31f05a6d8da610b9a270e7f79dac2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1712449Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Dan Clark <daniec@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#62902}