SharingGRDBTestSupport with assertQuery

[rcarver]

Adds SharingGRDBTestSupport as a new library, which exposes assertQuery such as from StructuredQueriesTestSupport.

However, the API is slightly different

1. It doesn't snapshot the SQL by default as its more common to look at db content only in this context.
2. It doesn't require an execute argument, as it uses @Dependency(\.defaultDatabase)

assertQuery(Reminder.all)  // Snapshots results only
assertQuery(               // Snapshots SQL + results
  includeSQL: true, 
  Reminder.all
)

I ended up just copying the implementation from StructuredQueries since printTable is private and its version of assertQuery would need to be modified for the includeSQL option. Could open those up with SPI if you think it's worth it?

[stephencelis]

What do you think of an optional database: Database? parameter like the @Fetch family of property wrappers, which defaults to this dependency?

[rcarver]

done!

[stephencelis]

@rcarver This looks good! But we got a test failure for assertQuery in release since we don't pretty-print queries in release mode. Want to wrap those tests in #if DEBUG?

[rcarver]

@stephencelis done! Confirmed it fixed via swift test -c release but I guess you have to kick off the CI in this repo?

[stephencelis]

Looks great, thanks!