Fix disabling utf-8 validation for nested types

[dnr]

What changed?
Fix #147 for nested types

Why?
See #147

How did you test it?
Also added unit test (just for rewrite code itself, not for effects)

[dnr]

I read through a bunch of the formatter/printer.. it looks like adding newlines in exactly the right places (and specifically adding more than there were before) is quite a lot more work. this is a pretty easy way to just get some newlines in there.

[cretz]

LGTM, but would personally like to see one test here and one in Go SDK:

• A test somewhere here but outside of the generator (i.e. in temporalproto package or something) that confirms, reusing one or more of our proto types, that string fields, map string keys, repeated strings, and a string in a nested message all marshal and unmarshal non-utf-8 as expected
• A test in Go SDK that confirms end-to-end that you can set something like a header key and/or a client identity to a non-utf8 string and that it works all the way through server and back on history.

(but neither are blocking)

[tdeebswihart]

LGTM, but would personally like to see one test here and one in Go SDK:

* A test somewhere here but outside of the generator (i.e. in `temporalproto` package or something) that confirms, reusing one or more of our proto types, that string fields, map string keys, repeated strings, and a string in a nested message all marshal and unmarshal non-utf-8 as expected

* A test in Go SDK that confirms end-to-end that you can set something like a header key and/or a client identity to a non-utf8 string and that it works all the way through server and back on history.

(but neither are blocking)

I plan to add to add tests all the way through our stack (sdk, server, etc) to make sure that everywhere we regenerate/use protos that we support this behavior