RFR: 8289743: AArch64: Clean up patching logic [v4]

[Andrew Haley]

> The current logic for patching is a mess of if-then-elses. By rearranging the logic and using a switch we can make it both easier to understand and faster.

Andrew Haley has updated the pull request incrementally with three additional commits since the last revision:

 - 8289743: AArch64: Clean up patching logic
 - 8289743: AArch64: Clean up patching logic
 - 8289743: AArch64: Clean up patching logic

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9398/files
  - new: https://git.openjdk.org/jdk/pull/9398/files/92016cb1..ed2a1bb6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9398&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9398&range=02-03

  Stats: 812 lines in 1 file changed: 547 ins; 187 del; 78 mod
  Patch: https://git.openjdk.org/jdk/pull/9398.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9398/head:pull/9398

PR: https://git.openjdk.org/jdk/pull/9398