RFR: 8306444: Don't leak memory in PhaseChaitin::PhaseChaitin

[Johan Sjölen]

Hi,

First, `PhaseChaitin::PhaseChaitin` used to create 4 resource array of size `_cfg.number_of_blocks`: one to store all of the block pointers in (`_blks`), and three to do a sorting of the blocks in some order. The latter three weren't freed in the constructor, causing them to hang around for the entire duration of the phase. This is unnecessary, so this patch frees the arrays when we're done with them. It also allocates all of the resources arrays in one go.

Second, it copied over each partially filled bucket into the `_blks`, one block at a time. This patch changes this so that we don't allocate the `_blks` resource array at all, instead we simply squash all of the partially filled buckets into the first one using `::memmove`. 

I haven't done any micro benchmarking, but this should be faster and take less space.

This is currently passing tier1.

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Commit messages:
 - Use nr_blocks in assert
 - Merge loops
 - Optimize PhaseChaitin

Changes: https://git.openjdk.org/jdk/pull/13533/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13533&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306444
  Stats: 37 lines in 1 file changed: 23 ins; 6 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/13533.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13533/head:pull/13533

PR: https://git.openjdk.org/jdk/pull/13533