RFR: 8337279: Optimize format instant [v6]

[Shaojin Wen]

> By removing the redundant code logic in DateTimeFormatterBuilder$InstantPrinterParser#formatTo, the codeSize can be reduced and the performance can be improved.

Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:

  breaking out the printNano methods

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20353/files
  - new: https://git.openjdk.org/jdk/pull/20353/files/87566614..ccbd6b5a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20353&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20353&range=04-05

  Stats: 24 lines in 1 file changed: 14 ins; 9 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20353.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20353/head:pull/20353

PR: https://git.openjdk.org/jdk/pull/20353