Make `peakPercentBu` a `cumulative` and `eq cumulative shift` param

[mgjarrett]

What is the change?

Add the categories "cumulative" and "eq cumulative shift" to the peakPercentBu parameter.

Why is the change being made?

Parameters that accumulate over multiple time steps need to be indicated as such in order to be handled correctly by some interfaces. Such parameters should be created as part of the "cumulative" category. Most parameters related to burnup were already marked as cumulative, but peakPercentBu was not.

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Checklist

• [x] This PR has only one purpose or idea.
• [ ] Tests have been added/updated to verify any new/changed code.

• [x] The code style follows good practices.
• [x] The commit message(s) follow good practices.

• [ ] The release notes have been updated if necessary.
• [x] The documentation is still up-to-date in the doc folder.
• [x] The dependencies are still up-to-date in pyproject.toml.