RFR: 8357649: IGV: add block index to the supplemental node properties

[Christian Hagedorn]

On Fri, 23 May 2025 13:42:12 GMT, Manuel Hässig <mhaessig at openjdk.org> wrote:

> This PR adds the block index to IGV node properties as soon as the CFG has been scheduled. This is really handy when working on peepholes, where one has to work with block indices.
> 
> ![Screenshot from 2025-05-23 15-35-29](https://github.com/user-attachments/assets/1a895e07-cf5f-4eed-afd0-08fe26cf0266)
> 
> Testing:
>  - [ ] [Github Actions](https://github.com/mhaessig/jdk/actions?query=branch%3AJDK-8357649-block-index)
>  - [ ] tier1, tier2, and some Oracle internal testing on Oracle supported platfors and OSs
> 
> Shout out to @robcasloz for coming up with an initial version of this patch.

Looks good to me, too!

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25414#pullrequestreview-2864736108