[6.3.0] Teach ijar about dynamic constants.

[iancha1992]

Teach ijar about dynamic constants.

Fixes #18360

Closes #18406

Commit 69d2991

PiperOrigin-RevId: 540750474
Change-Id: If61bcaaf018b92a1bf87335c1075c28294932b1f

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[cushon]

@iancha1992 this PR was already imported: 69d2991

edit: I missed this was for the 6.3.0 branch, sorry

[iancha1992]

@benjaminp our team is trying to cherry-pick this for release-6.3.0. However, looks like in order to merge your work, we have to have you sign the Contributor License Agreement (CLA), which is a one-time process, and only takes a minute. Please refer to this: https://github.com/bazelbuild/bazel/pull/18711/checks. Thank you

[benjaminp]

Somehow 69d2991 was imported/exported under my personal email rather than my work email, which is listed under a corporate CLA. Perhaps you can change the address of the commit in this PR? (See any of my other commits in this repository for it.)

[iancha1992]

Closing this PR because I just amended the commit's author email for CLA compliance. There is another PR #18729