RFR: 8356949: AArch64: Tighten up template interpreter method entry code

[Chad Rakoczy]

[JDK-8356949](https://bugs.openjdk.org/browse/JDK-8356949)

This change is the aarch64 version of [JDK-8352415](https://bugs.openjdk.org/browse/JDK-8352415). 

To improve interpreter performance, which is important for faster startup, the method entry code was refactored to reuse some memory accesses and also spread them out to allow more latency-hiding hardware mechanisms to kick in.

Additional testing:

- [x] Ad-hoc -Xint benchmarks
- [x] Linux aarch64 server fastdebug, tier 1/2/3/4

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Commit messages:
 - Name r5 for readablity
 - Remove load_mirror

Changes: https://git.openjdk.org/jdk/pull/25312/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25312&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356949
  Stats: 17 lines in 1 file changed: 9 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/25312.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25312/head:pull/25312

PR: https://git.openjdk.org/jdk/pull/25312