Valhalla JVMCI update

[MichaelHaas99]

Provides a JVMCI compiler with the following information:

• value class semantics (identity flag, ValueObjectMethods etc.)
• acmp profiling data
• calling and return convention for value objects
• null-restricted heap flattening of fields and arrays

To put this PR out of draft state the following steps are necessary:

• rebase
• remove the ImplicitlyConstructible concept
• update the interface according to the heap flattening for JEP401 (atomic, nullable etc.)
• also implement functionalities for other architectures other than x64
• provide access to profiling data of the aaload and aastore bytecodes
• test the JVMCI changes
• remove the modifications made in the JTREG test cases

---

Progress

• Change must not contain extraneous whitespace

Error

 ⚠️ OCA signatory status must be verified

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/1493/head:pull/1493
$ git checkout pull/1493

Update a local copy of the PR:
$ git checkout pull/1493
$ git pull https://git.openjdk.org/valhalla.git pull/1493/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1493

View PR using the GUI difftool:
$ git pr show -t 1493

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/valhalla/pull/1493.diff

[bridgekeeper]

Hi @MichaelHaas99, welcome to this OpenJDK project and thanks for contributing!

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[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@MichaelHaas99 this pull request can not be integrated into lworld due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout mh/GR-57655
git fetch https://git.openjdk.org/valhalla.git lworld
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge lworld"
git push