[epic] Replace schema with pico

[rbalicki2]

We have functions that mutate the schema. That is fundamentally incompatible with pico, which requires that functions are pure. Well, mutating parameters isn't that!

So, instead, in the DB we should basically store all the fields that we are currently using the schema for.

Consider generating a reader AST from

field Query.Foo {
  bar {
    baz
  }
}

We would have the following call tree:

• get_parsed_iso_literal(someIdentifier)
• get_type("Query") -> query_object_id
  • parse_graphql_schema
    • schema file input
• get_field(query_object_id, "Foo") -> ensure there are no collisions? Idk tbh
  • parse_graphql_schema
    • schema file input
• get_field(query_object_id, "bar") -> bar_object_id, ensure it's an object etc
  • parse_graphql_schema
    • schema file input
• get_field(bar_object_id, "baz") -> ensure it's a scalar

Key takeaways:

• at no point do we validate everything, ideally including in the "parse_graphql_schema" step, e.g. we can proceed, even if there's another iso literal in a bad state
• there is no schema, just free functions
• it may also mean that selection sets are not stored on the client field/pointer, and fields are not stored on schema objects