Performance issue with MethodHandle.asCollector

See discussion here:

https://mail.openjdk.java.net/pipermail/mlvm-dev/2021-March/006895.html

MethodHandles.collectArguments with an appropriate filter function is faster than MethodHandle.asCollector, which appears to copy arrays under some circumstances.

The code of MethodHandles.collectArguments and MethodHandle.asCollector is very similar (unsurprisingly), perhaps indicating some localized adjustment to the latter may be possible to fix the issue.