* consensus/misc, params: add EIP-4844 blobfee conversions

* consensus/misc: pull in fakeExponential test cases

* consensus/misc: reuse bigints

* consensus/misc: nit renames, additional larger testcase

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Co-authored-by: Roberto Bayardo <bayardo@alum.mit.edu>
Co-authored-by: Martin Holst Swende <martin@swende.se>