RFR: 8330159: [C2] Remove or clarify Compile::init_start [v6]

[Dean Long]

On Tue, 3 Sep 2024 13:49:51 GMT, Yagmur Eren <duke at openjdk.org> wrote:

>> Compile::init_start method contained only an assertion. To cleanup, this method is removed and the locations where this method is called are replaced with the corresponding assertion. See issue: [JDK-8330159](https://bugs.openjdk.org/browse/JDK-8330159)
>
> Yagmur Eren has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update Compile::verify_init comment

Marked as reviewed by dlong (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/20715#pullrequestreview-2283968926