RFR: JDK-8261510: Use RFC numbers rather than protocol or draft names in sun.security.ssl.SSLExtension [v2]

[John Jiang]

> This is a simple cleanup for sun.security.ssl.SSLExtension.
> It converts protocol or draft names to RFC numbers correspondingly.
> It also removes a trailing space in extension token_binding, and move signature_algorithms_cert to RFC 8446 extension group.

John Jiang has updated the pull request incrementally with one additional commit since the last revision:

  Addressed Xuelei's comment

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2517/files
  - new: https://git.openjdk.java.net/jdk/pull/2517/files/7209b2b7..84f131c0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2517&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2517&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2517.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2517/head:pull/2517

PR: https://git.openjdk.java.net/jdk/pull/2517