This change refactors the v8.h API as discussed in
https://docs.google.com/document/d/1yuXgNHSbTAPubT1Mg0JXp5uTrfirkvO1g5cHHCe-LmY/edit#heading=h.q0c9h4p928mn
such that a v8::Module exposes module requests as a FixedArray of
ModuleRequest objects, which can then be used to obtain their module
specifier and source code offset.  This replaces the old functions that
passed back individual specifier Strings and Locations via repeated
calls to getters that take an index.  These are marked as deprecated.

The new ModuleRequest interface includes a getter for an
ImportAssertions FixedArray, which will contain the import assertions
for the request if --harmony-import-assertions is set, and will be
empty otherwise.

One notable change here is that the APIs now return source code offsets
rather than v8::Locations.  The host must then call the new
Module::SourceOffsetToLocation to convert these offsets into line/column
numbers. This requires a bit more back-and-forth, but allows the host to
defer the cost of converting from source offset to line/column numbers
until an error needs to be reported, potentially skipping the work
altogether.

Bug: v8:10958
Change-Id: I181639737c701e467324e6c781aa4d7bdd87ae8c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2545577
Commit-Queue: Dan Clark <daniec@microsoft.com>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71387}