Assign ctx, fs, sel to _ so no warnings about unused variables

[halkeye]

alternative to #2999

Found a few more while doing development, gopls/vscode was warning about more variables that are undefined.
Instead of having even more complex logic for making variables _, just assigned them to nothing so they would get used.

That only leaves one left in generate.go for me

I have:

• Added tests covering the bug / feature (see testing)
• Updated any relevant documentation (see docs)

[StevenACoffman]

I would much rather we don't do this. The point of the linter warning you is to detect possible bugs where an argument or a variable declaration are unused, and it identified we were being a bit lazy in our codegen conditionals.

When the arguments are changed from ctx to _ it is clear we only have the extraneous argument so the signature will match an interface.

When we assign var _ = ctx it obscures this intention.

[StevenACoffman]

Closing in favor of #2999

[halkeye]

Yea. That's totally cool. One of the arguments was only used inside a loop behind a conditional and I couldn't figure out how to nicely figure that out in the args, so this was idea b

I'll see if I can't find a way. Thanks