childkey tax rate

[open-junius]

Description

CHK Tax Rate is a recycle fee applied to all CHKs outside of the same cold key
New sudo global param for setting CHK Tax Rate
Default CHK Tax Rate set to 18% (meaning 18% recycle fee applied to all CHKs outside of the same cold key)
Validators can still set CHK Take, which functions as it does now, but applies net of the tax (ie. after the recycle fee is taken)
Separate PR from the one force enabling CR4/BT9.9.2+, but to be included in the same merge as a one-two-punch against WC/CHK.

Related Issue(s)

• Closes #[issue number]

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

If this PR introduces a breaking change, please provide a detailed description of the impact and the migration path for existing applications.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Additional Notes

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[open-junius]

close it as it is the same as #1996