ch4: revise MPIR_CVAR_CH4_GLOBAL_PROGRESS

[hzhou]

Pull Request Description

Make the CVAR to accept enums values of normal, low, and high.

[skip warnings]

Author Checklist

• [x] Provide Description Particularly focus on why, not what. Reference background, issues, test failures, xfail entries, etc.
• [x] Commits Follow Good Practice Commits are self-contained and do not do two things at once. Commit message is of the form: module: short description Commit message explains what's in the commit.
• [ ] Passes All Tests Whitespace checker. Warnings test. Additional tests via comments.
• [x] Contribution Agreement For non-Argonne authors, check contribution agreement. If necessary, request an explicit comment from your companies PR approval manager.

[hzhou]

test:mpich/custom netmod: ch4:ofi config: vci