RFR: 8250668 : Clean up method_oop names in adlc

[John Tortugo]

Relates to: https://bugs.openjdk.java.net/browse/JDK-8250668
Tested on: x86_64 {windows, linux, os x} x {jdk-tier1-part1..3, hotspot-tier1-gc}
Follow up from this thread: https://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-September/039846.html

Rename occurrences of 'method_oop' under `src/` to just `method'.

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Commit messages:
 - Rename 'method_oop' references to just 'method'

Changes: https://git.openjdk.java.net/jdk/pull/164/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=164&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8250668
  Stats: 61 lines in 15 files changed: 4 ins; 0 del; 57 mod
  Patch: https://git.openjdk.java.net/jdk/pull/164.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/164/head:pull/164

PR: https://git.openjdk.java.net/jdk/pull/164