RFR: 8349457: [leyden] Workaround Leyden problems with -XX:-TieredCompilation [v2]

[Aleksey Shipilev]

> Currently, supplying `-XX:-TieredCompilation` would break with Leyden workflows, because the archive-backed code cache heap would only be created if `SegmentedCodeCache` is enabled. With default compilation policy, this happens normally when tiered compilation is enabled, but not without it.
> 
> There are other minor peculiarities that we need to handle, which are exposed with `runtime/cds` + `-XX:-TieredCompilation` runs.
> 
> This prevents us from testing C2-only Leyden configs and studying compilation dynamics without tiered policy getting in the way.
> 
> Additional testing:
>  - [x] Ad-hoc Leyden experiments now work with `-XX:-TieredCompilation`: the C2-only code is being stored and loaded successfully from the CDS archive
>  - [x] `runtime/cds` now passes with `-XX:-TieredCompilation`
>  - [x] `runtime/cds` still passes by default (i.e. with tiered compilation)

Aleksey Shipilev 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 three additional commits since the last revision:

 - Merge branch 'premain' into JDK-8349457-enable-c2
 - More fixes
 - Fix

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

Changes:
  - all: https://git.openjdk.org/leyden/pull/32/files
  - new: https://git.openjdk.org/leyden/pull/32/files/0dcee32d..1ee3b847

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=leyden&pr=32&range=01
 - incr: https://webrevs.openjdk.org/?repo=leyden&pr=32&range=00-01

  Stats: 57620 lines in 3321 files changed: 26973 ins; 16639 del; 14008 mod
  Patch: https://git.openjdk.org/leyden/pull/32.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/32/head:pull/32

PR: https://git.openjdk.org/leyden/pull/32