RFR: Allow heuristic trigger to increase capacity instead of running a collection

[William Kemper]

Before the adaptive heuristic starts a collection, it will attempt to increase the capacity of its generation. If the capacity is increased, the heuristic will re-evaluate the trigger criteria.

There is also a change here to attempt to increase the size of the old generation in response to a promotion failure.

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Commit messages:
 - Remove trailing whitespace
 - Centralize resetting gc learning count, increase old for first promotion failure.
 - Use consistent assertions for locking or safepoint
 - WIP: Allow heuristics to resize generation instead of collecting
 - Capacity changes should also apply to adjusted capacity

Changes: https://git.openjdk.org/shenandoah/pull/190/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=190&range=00
  Stats: 97 lines in 10 files changed: 73 ins; 9 del; 15 mod
  Patch: https://git.openjdk.org/shenandoah/pull/190.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah pull/190/head:pull/190

PR: https://git.openjdk.org/shenandoah/pull/190