RFR: 8350097: Make Compilation::current() and Compile::current() safer

[Thomas Stuefe]

On Fri, 14 Feb 2025 17:57:31 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Context: I think `ciEnv` is pretty compiler-agnostic, and it would be better to avoid exposing the fact C1/C2 exist to that interface, even if only for asserts. Seems cleaner to check that we are calling `Compilation::current()` from C1 and `Compile::current()` from C2.
>
> I agree with Aleksey here.

Yes, I like this too. Simpler. Okay, I try that.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23635#discussion_r1956588610