ART: Adds an entrypoint for invoke-custom

Add support for the compiler to call into the runtime for
invoke-custom bytecodes.

Bug: 35337872
Test: art/test.py --host -r -t 952
Test: art/test.py --target --64 -r -t 952
Test: art/test.py --target --32 -r -t 952
Change-Id: I821432e7e5248c91b8e1d36c3112974c34171803