RFR: 8323601: Improve LayoutPath.PathElement::toString [v3]

[Per Minborg]

> This PR proposes to add an improved Improve `LayoutPath.PathElement::toString` method simplifying debugging.
> 
> Opinions and suggestions for `static PathElement sequenceElement(long start, long step)` are welcome.

Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Rename local variable
 - Merge branch 'master' into layout-path-tostring
 - Rework PathElement:toString
 - Add toString to PathElement

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17417/files
  - new: https://git.openjdk.org/jdk/pull/17417/files/83cf10c5..269523b8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17417&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17417&range=01-02

  Stats: 21865 lines in 781 files changed: 12172 ins; 6978 del; 2715 mod
  Patch: https://git.openjdk.org/jdk/pull/17417.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17417/head:pull/17417

PR: https://git.openjdk.org/jdk/pull/17417