RFR: 8357434: x86: Simplify Interpreter::profile_taken_branch

Wed May 21 08:28:27 UTC 2025

Noticed that `Interpreter::profile_taken_branch` has the same `sbbptr` pattern we have eliminated with [JDK-8356946](https://bugs.openjdk.org/browse/JDK-8356946). The same logic applies here: the counter is 64-bit, never practically overflows, and no other code cares about it.

Also tidied up some comments around it.

Additional testing;
 - [x] Linux x86_64 server fastdebug, `tier1 tier2`

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/25343/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25343&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357434
  Stats: 16 lines in 3 files changed: 0 ins; 11 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/25343.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25343/head:pull/25343

PR: https://git.openjdk.org/jdk/pull/25343