RFR: 8316305: Initial buffer size of StackWalker is too small caused by JDK-8285447 [v4]

[Mandy Chung]

> A trivial fix.   [JDK-8285447](https://bugs.openjdk.org/browse/JDK-8285447) intends to change the initial batch size only for a stack walker with an estimated stack depth. For stack walkers without user-supplied estimated stack depth, the initial batch size is changed to 3 which is a bug.  This causes the stack walker to fetch the second batch after walking 2 frames.

Mandy Chung has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:

 - Merge branch 'master' of https://github.com/openjdk/jdk into JDK-8316305
 - Revert this change. PR 15876
 - Fix a warning caused by 8316456
 - Merge
 - Merge branch 'master' of https://github.com/openjdk/jdk into JDK-8316305
 - 8316305: Initial buffer size of StackWalker is too small caused by JDK-8285447

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Changes: https://git.openjdk.org/jdk/pull/15749/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15749&range=03
  Stats: 8 lines in 1 file changed: 1 ins; 2 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/15749.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15749/head:pull/15749

PR: https://git.openjdk.org/jdk/pull/15749