Update Actions and Filters to be named consistenty

[jasonbahl]

currently the codebase has actions and filters with mixed naming conventions:

Some start with wpgraphql_cache (such as wpgraphql_cache_save_request) and some start with graphql_cache such as graphql_purge).

We should decide which prefix to use and make things consistent.

Note, we'll need to keep around the old actions/filters and deprecate them as folks could already be using them.

Some helpful info re: deprecating in here: https://juagonala.com/how-to-deprecate-code-in-wordpress/

[jasonbahl]

Note: the linter gets grumpy if we use graphql_cache instead of wpgraphql_cache (see: https://github.com/wp-graphql/wp-graphql-smart-cache/actions/runs/5555942329/jobs/10147786949?pr=230#step:7:20)

So whatever decision we make, we need to update the linter accordingly

[jasonbahl]

WPGraphQL for ACF recently made the change to using forward slashes in action and filter names.

see: wp-graphql/wpgraphql-acf#67

I think it would be good to implement this style for WPGraphQL Smart Cache as it makes things more readable (at least in my opinion) and I can more clearly understand the "domain" the hook is related to.

Something like:

wpgraphql/smart-cache/$action_name

or

wpgraphql/cache/$action_name

(not 💯 sold either way on "smart-cache" vs "cache" 🤷🏻‍♂️ )