Add blacklist support for partial writing

[stephenberry]

We should be able to optionally exclude fields when writing structs from the write calls, besides utilities like glz::hide

[amosbird]

Can we add support for partial writing with a dynamically specified set of whitelist/blacklist fields and globs? I’m trying to use Glaze to implement response filtering functionality as described in Elasticsearch's common options documentation.

Thank you!

[stephenberry]

@amosbird, dynamic partial writing is definitely desired. A long term goal is to support JMESPath, which would also require this support.

The reflection system in Glaze already provides an array of keys and a tuple of values, we just need to write a higher level of abstraction over glz::reflect so that we can more easily iterate at runtime. I'll keep your comment in mind as I continue to brainstorm the best approach.