Generate `ToMaybe` in `deriveEsqueletoRecord`

[halogenandtoast]

replaces #370

• [ ] Bumped the version number.
• [ ] Documented new APIs with Haddock markup.
• [ ] Added @since declarations to the Haddock.
• [ ] Ran stylish-haskell and otherwise adhered to the style guide.

After submitting your PR:

• [ ] Update the Changelog.md file with a link to your PR.
• [ ] Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts).

[halogenandtoast]

Opening this up for conversation since the draft didn't get eyes and I think this is nearly there.

[halogenandtoast]

@parsonsmatt did you mean something different from: https://github.com/bitemyapp/esqueleto/pull/378/files#diff-bef0a2133965554f3b49d699a015a29f235548c9ae5edc52ce80cd348332720dR282-R300

[halogenandtoast]

Confirmed this compiles and all existing tests run and pass on 8.10.7

[halogenandtoast]

I don't have a machine I can run 8.6.5 on until November 4th so fixing this will have to wait until then unless someone else can do the update here.