Refactor: Consistently use either pointer or value receivers

[cbandy]

Subtle bugs can arise when mixing the two. A type is more coherent when it behaves as only one of (1) a value or (2) a reference.

A new linter identifies this situation but does not yet account for unmarshal methods on value types.

Checklist:

• [x] Have you added an explanation of what your changes do and why you'd like them to be included?
• [x] Have you updated or added documentation for the change, as applicable?
• [x] Have you tested your changes on all related environments with successful results, as applicable?
  • [x] Have you added automated tests?

Type of Changes:

• [x] Other

Other Information:

See https://go.dev/wiki/CodeReviewComments#receiver-type and https://go.dev/wiki/MethodSets