[epic] Deferred normalization ASTs

[rbalicki2]

• Depends on #33

Background: entrypoint artifacts and normalization ASTs

• For each iso(`entrypoint Type.Field`) literal that the compiler encounters, it will generate a Type/Field/entrypoint.ts file.
• This file currently (i.e. pre #33) contains a query text and a normalization AST.
• The query text is used when making the query
• The normalization AST is (currently) only used to write the network response into the key-value store and for garbage collection (which is also only done after the network response is received).
  • They will (after #42) be used to determine whether a network request needs to be made.
• Because the normalization AST is only used after a network response is received, we can fetch the normalization AST later (e.g. when making the network request).

This epic

• This epic is to load normalization ASTs when the network request is created, via https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/import or something.
• This should be controllable with a directive on the entrypoint
  • So, the iso literal parser should be modified to include support for parsing directives
• Whether the normalization AST is hard-loaded should be reflected in the type of the entrypoint, since the entrypoint cannot be used with an if-necessary fetch policy if the normalization AST is not present.
  • One should be able to eventually call entrypoint.loadNormalizationAst().then(entrypointWithNormalizationAst => fetchIfNecessary(...)) or the like