[lworld] RFR: 8369893: [lworld] Split multiple @run statements in runtime tests into separate @test blocks

[Paul Hübner]

Hi all,

This PR mirrors the changes made to [the compiler](https://github.com/openjdk/valhalla/pull/1681) `jtreg` testing setup ([issue](https://bugs.openjdk.org/browse/JDK-8369437)).

**Concretely:**
* Split multiple (independent) `@run`s into separate `@test` blocks, specifying new IDs where appropriate.
* Added packages where we missed them for consistency. This excludes places where the test setup does not allow for packages or for tests that are disabled (some of which don't compile, as our model is evolving). 
* Changed `@run main/othervm` into `@run main` when there was no flag passed.

**Impact:**

I compared machine execution time in tiers 1-4 to `jdk-26-valhalla+1-89` (which my changes are based on). 

| | lworld | lworld + patch | improvement
-- | -- | -- | -- 
tier1 | 1d 00h 26m 16s |  1d 00h 13m 20s | ~ - 3 mins
tier2 | 1d 03h 16m 04s | 1d 01h 24m 05s | ~ -2 hours
tier3 | 2d 17h 29m 13s | 2d 17h 16m 15s | ~ -13 mins
tier4 | 2d 11h 32m 26s | 2d 01h 05m 40s | ~ -10 hours

Overall, the trend shows shorter execution times. (And by extension, probably less electricity usage too :))

Note that the CI ran a few extra tasks at tiers 2,  (two orders of magnitude less compared to the total number of tasks) than my personal run did. I don't think these will impact the results significantly.

*Disclaimers: these measurements were run before adding packages and getting rid of a few leftover `main/othervm`, although these should not change the results significantly. Also, this is very ad-hoc "benchmarking," variance is not measured.*

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

Commit messages:
 - Add package and fix some left over othervm.
 - Refactor ValueTearing.java.
 - TestFlatArrayElementMaxOops.java.
 - Refactor ObjectMethods.java.
 - Refactor InlineTypesTest.java.
 - Refactor InlineTypeDensity.java.
 - Refactor InlineTypeArray.java.
 - First iteration, othervm removal and trivial splits.

Changes: https://git.openjdk.org/valhalla/pull/1682/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1682&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369893
  Stats: 418 lines in 52 files changed: 279 ins; 1 del; 138 mod
  Patch: https://git.openjdk.org/valhalla/pull/1682.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1682/head:pull/1682

PR: https://git.openjdk.org/valhalla/pull/1682