RFR: 8260053: Optimize Tokens' use of Names [v2]

[Guoxiong Li]

> Hi all,
> 
> This patch initializes the names about `TokenKind` at the beginning of the constructor of the class `Names`. As a result, the `Tokens.maxKey` and the length of the array `Tokens.key` become small. By using this patch, the length of the array `Tokens.key` is changed from 4280 to 383.
> 
> The original discussion is at [compiler-dev](https://mail.openjdk.java.net/pipermail/compiler-dev/2021-January/016126.html).
> 
> Thank you for taking the time to review.
> 
> Best Regards.

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Use Map<String, TokenKind>

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2169/files
  - new: https://git.openjdk.java.net/jdk/pull/2169/files/5470a4ee..5bbf949f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2169&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2169&range=00-01

  Stats: 47 lines in 2 files changed: 6 ins; 35 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2169.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2169/head:pull/2169

PR: https://git.openjdk.java.net/jdk/pull/2169