RFR: 8295302: Do not use ArrayList when LambdaForm has a single ClassData [v4]

[Ioi Lam]

> Please review this small optimization. As shown in the JBS issue, most of the generated LambdaForm classes have a single ClassData, so we can get a small footprint/speed improvement.

Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Merge branch 'master' into 8295302-no-arraylist-for-single-classdata-for-lambdaform
 - javadoc from @mlchung; fix code format per @turbanoff
 - Merge branch 'master' into 8295302-no-arraylist-for-single-classdata-for-lambdaform
 - @mlchung comments
 - @iwanowww comments
 - 8295302: Do not use ArrayList when LambdaForm has a single ClassData

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10706/files
  - new: https://git.openjdk.org/jdk/pull/10706/files/eb05b9ef..51f18357

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10706&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10706&range=02-03

  Stats: 5201 lines in 617 files changed: 2471 ins; 1039 del; 1691 mod
  Patch: https://git.openjdk.org/jdk/pull/10706.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10706/head:pull/10706

PR: https://git.openjdk.org/jdk/pull/10706