RFR: 8295302: Do not use ArrayList when LambdaForm has a single ClassData [v2]

[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 incrementally with one additional commit since the last revision:

  @iwanowww comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10706/files
  - new: https://git.openjdk.org/jdk/pull/10706/files/793f24ce..5a800f0d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10706&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10706&range=00-01

  Stats: 11 lines in 1 file changed: 0 ins; 7 del; 4 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