[vm] Allow optimized type testing stubs to be partial.

Previously, the code in the TypeCheck runtime entry assumed that if a
lazily specialized type testing stub (TTS) returned a false negative in
JIT mode, that it should always be regenerated and that regeneration
would always result in different code. In AOT mode, false negatives
instead always cause the stub to go to runtime, even if that false
negative had been seen before, because the assumption is that false
negatives shouldn't happen when the whole class hierarchy is known at
compile time.

However, even in the current implementation of optimized TTSes, there
are cases where this assumption is false. For example, the code
generated by BuildOptimizedSubclassRangeCheckWithTypeArguments allows
for provided type arguments to be type parameters. When this happens,
the type parameter is instantiated at runtime using the instantiator or
function type arguments, and the instantiated type parameter must be
identical to the result retrieved from the type arguments of the
instance. That means that if the instantiated type parameter is not the
same type, but a supertype, of the result, then a false negative is
generated.

This CL changes TypeCheck's handling of false negatives from lazily
specialized TTSes as follows: in JIT, if the regenerated stub is the
same as the old stub, or in AOT, a false negative causes the same fall
back to SubtypeTestCaches as unoptimized stubs.  This way, further
checks with the same false negative will be caught via the STC before
going to runtime, assuming the STC hasn't already filled up with false
negatives.

Currently, we only generate false negatives for reasons that will not
change when respecialization occurs due to additions to the hierarchy,
so we do not need to clear affected STCs during respecialization.
However, the previous approach to resetting STCs on reload (in
CallSiteResetter::ResetCaches) is insufficient, since there may be
caches containing reloaded types in non-reloaded code (like the TTS
invoker stub created by the TTS testing framework). Instead, clear
all caches on reload using the same ObjectVisitor as deoptimizing type
testing stubs.

Since we now have to check instruction equality to determine whether
to add to the STC, we now only replace the existing stub if the
instructions are different. This makes it easier to test whether a
TTS invocation on a false positive caused respecialization or not.

This CL also reworks the testing framework for type testing stubs,
1) creating a test case object that stores the particulars of a given
invocation, including expectations, and 2) moving most checks and
access to appropriate data structures into a state object that handles
setup and performing invocations given test cases.

TEST=vm/cc/TTS_Partial

Cq-Include-Trybots: luci.dart.try:vm-kernel-linux-release-x64-try,vm-kernel-precomp-linux-release-x64-try,vm-kernel-precomp-nnbd-linux-release-x64-try,vm-kernel-nnbd-linux-release-x64-try,vm-kernel-tsan-linux-release-x64-try,vm-kernel-linux-product-x64-try,vm-kernel-precomp-linux-product-x64-try,vm-kernel-linux-release-simarm-try,vm-kernel-linux-release-simarm64-try
Change-Id: I139608c5a0f2442a85a1cf39d1c04104db7a5593
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/208653
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>

• runtime/lib/object.cc[diff]
• runtime/vm/compiler/backend/il_test_helper.cc[diff]
• runtime/vm/compiler/backend/il_test_helper.h[diff]
• runtime/vm/object.cc[diff]
• runtime/vm/object.h[diff]
• runtime/vm/object_reload.cc[diff]
• runtime/vm/runtime_entry.cc[diff]
• runtime/vm/type_testing_stubs.cc[diff]
• runtime/vm/type_testing_stubs.h[diff]
• runtime/vm/type_testing_stubs_test.cc[diff]