Make the Compressor work with spaces other than LOS

[k-sareen]

Currently the Compressor implementation merged in #1340 only updates pointers in the CompressorSpace and LOS. While this works for OpenJDK (its only currently supported binding), it doesn't work generally since we may have a non-moving space that needs to be updated as well. I'm not sure how this could be accomplished without a write-barrier capturing pointers into the CompressorSpace.

MarkCompact works by having another transitive closure wherein pointers into the MarkCompactSpace get updated with the forwarded values, but implementing this in the Compressor is a non-starter since the whole appeal of the algorithm is that it doesn't perform extra traces, only working off of a mark bitmap.

Cc @no-defun-allowed.

[no-defun-allowed]

Can we remember out-of-CompressorSpace -> in-CompressorSpace references while tracing, like Ben-Yitzhak et al do for compacting only parts of their heap and fixing references for the rest?