RFR: Fix fullgc assertion

[Kelvin Nilsen]

Relax generation sizing assertions during Full GC because of the sequencing of operations that occur during Full GC.

Enforce the assertion constraints at the end of Full GC.

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Commit messages:
 - Fix white space
 - Merge remote-tracking branch 'GitFarmBranch/fix-fullgc-assertion-error' into fix-fullgc-assertion
 - Fix assertion failure during Full GC

Changes: https://git.openjdk.org/shenandoah/pull/200/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=200&range=00
  Stats: 15 lines in 2 files changed: 13 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/shenandoah/pull/200.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah pull/200/head:pull/200

PR: https://git.openjdk.org/shenandoah/pull/200