Clean up `RegTypeCache::FromDescriptor()` arguments.

Only tests passed `true` as `precise` and most of them do
not really care about that anyway. For the two that do, we
implement a helper function to get a precise `j.l.Object`
reference type the way we would get it for `new Object()`.
Remove the `precise` argument and change the `ClassLoader`
argument to `Handle<>` (also for other functions) to avoid
unnecessary `Handle<>` decoding and re-encoding.

Also clean up `RegTypeCache:From()` which has only one
non-test caller, namely `RegTypeCache::FromDescriptor()`.
Make it private and similarly remove the `precise` argument.
Change tests to use `FromDescriptor()` instead.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: Iab68aea975ec57899d74c728130ece852a810ae7
4 files changed