RFR: 8315413: Remove special filtering of Continuation.yield0 in StackWalker

[Mandy Chung]

Loom added a special filtering of Continuation.yield0 in stack walker.  After the initial implementation, JDK-8304919 marks the yielding and entering methods with `@Hidden` and hidden frames are filtered by stack walker by default.   With `@Hidden` the special filtering should not be needed.

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Commit messages:
 - 8315413: Remove special filtering of Continuation.yield0 in StackWalker

Changes: https://git.openjdk.org/jdk/pull/15498/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15498&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315413
  Stats: 33 lines in 4 files changed: 0 ins; 24 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/15498.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15498/head:pull/15498

PR: https://git.openjdk.org/jdk/pull/15498