log redaction: make redactability lints opt-out instead of opt-in

[dhartunian]

Is your feature request related to a problem? Please describe.
Currently, we do not enforce redactability on new types. This reduces the fidelity of redactable logs in CRDB.

Describe the solution you'd like
via @tbg on #65453:

Some design work upfront would be needed here, but the lint passes in ./pkg/lint/passes are probably a good starting point. We could traverse the syntax trees and to investigate everything that is passed to a logging method (to see whether it implements redactability), but that may be incomplete (redaction might be important outside of logging). The easier, and perhaps also more helpful option, is to check all the types declared by cockroach code (i.e. inside of our repo and not in vendor) directly for whether the implement redaction. To get the linter in without having to boil the ocean, we allow exceptions (type foo struct {} // nomustredact) which would be implemented similar to here or here - I prefer the latter since I understand it; the former seems to misfire sometimes. We want two lint exceptions, nomustredact, and todomustredact. The idea is that to get the lint to pass, we add // todomustredact everywhere and count how many we added. We configure the linter to allow no more than that number of todomustredact tags, and also output the current number. This gives us a metric that we can optimize, and an easy way to find all the types that still need to be retrofitted. Thanks to code ownership (go run ./pkg/cmd/whoownsit), we could break that down on a per-team level as well (i.e. team that owns the file that declares the type owns the redactability of the type), for scheduling this work into the next release.

This is part of #65453

Jira issue: CRDB-7897

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