RFR: 8340205: Native linker allows MemoryLayout consisting of only PaddingLayout [v8]

[Per Minborg]

> This PR prevents sequence layout with padding to be used with the Linker.

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 17 additional commits since the last revision:

 - Rephrase liker arg requirements
 - Merge branch 'master' into linker-padding-layout-only
 - Add rule checkings in AbstractLinker and add tests
 - Merge branch 'master' into linker-padding-layout-only
 - Update Linker docs
 - Merge branch 'master' into linker-padding-layout-only
 - Reword doce
 - Add to specification and refine detection of PL GLs
 - Add specific message for group layouts with only padding layouts
 - Merge branch 'master' into linker-padding-layout-only
 - ... and 7 more: https://git.openjdk.org/jdk/compare/77b221ef...0f4e93ff

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21041/files
  - new: https://git.openjdk.org/jdk/pull/21041/files/8e4ee286..0f4e93ff

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21041&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21041&range=06-07

  Stats: 62307 lines in 1174 files changed: 16151 ins; 41965 del; 4191 mod
  Patch: https://git.openjdk.org/jdk/pull/21041.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21041/head:pull/21041

PR: https://git.openjdk.org/jdk/pull/21041