chore(graphql): segregate graphql toolshed module

[LNSD]

As discussed and agreed in a Slack discussion:

[...]
something as involved as a GraphQL parser probably should be it’s own crate as well.

So, in this PR:

• Segregate the GraphQL module into its own crate.
• Deprecate the toolshed's graphql module in favor of the new graphql crate.

Additionally, these changes align with the GraphQL client work in #9.

[Theodus]

Looks good. Not sure we even need to bother with deprecation. I think we could just remove the old graphql module immediately.

[LNSD]

Looks good. Not sure we even need to bother with deprecation. I think we could just remove the old graphql module immediately.

I'd rather do it in 2 steps, so we have an intermediate stage where both modules contain the code, and we can do some tests.