Extend type assertions to all types covering JavaScript values.
This is achieved by allocating type representations on the heap using
newly defined HeapObject subclasses. To allocate these in the compiler,
we disable concurrent compilation for the --assert-types flag for now.

Fix two type errors that came up with the existing tests:
1. JSCreateKeyValueArray has type Array (i.e., a JSArray) instead of
   OtherObject.
2. OperationTyper::NumberToString(Type) can type the result as the
   HeapConstant Factory::zero_string(). However, NumberToString does
   not always produce this string. To avoid regressions, the CL keeps
   the HeapConstant type and changes the runtime and builtin code to
   always produce the canonical "0" string.

A few tests were failing because they check for truncations to work
and prevent deoptimization. However, AssertType nodes destroy all
truncations (which is by design), so these tests are incompatible
and now disabled for the assert_types variant.

Drive-by fix: a few minor Torque issues that came up.

Change-Id: If03b7851f7e6803a2f69edead4fa91231998f764
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3234717Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77565}