RFR: 8259228: Zero: rewrite (put|get)field from if-else chains to switches

[Aleksey Shipilev]

Current handling for (put|get)field uses if-else chain to select the access type. This can be made more uniform by using switches, like accessor_entry code already does.

Additional testing:
  - [x] Ad-hoc Zero performance tests

-------------

Commit messages:
 - 8259228: Zero: rewrite (put|get)field from if-else chains to switches

Changes: https://git.openjdk.java.net/jdk/pull/1943/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1943&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259228
  Stats: 132 lines in 1 file changed: 54 ins; 0 del; 78 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1943.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1943/head:pull/1943

PR: https://git.openjdk.java.net/jdk/pull/1943