Add this as a self type

[HT154]

Depends on #1796

This PR:

• Adds type this, a fully featured self type for use in modules or classes.
  • Forbids use of this in typealias bodies.
• Deprecates usage of the module type in const scopes (class and typealias bodies, annotations, const properties/methods) with a warning, to be an error in a future release.
  • In some cases this induces incorrect or undefined behavior (see module types as typelias type args are evaluated in the context of the alias's module, not where module is used #1712).
  • Usages should either be replaced by this or a self-import and use of the current module.
• Adopts this in the standard library:
  • pkl.base#Any.getClass() now returns Class<this>.
  • pkl.base#Any.ifNonNull() now accepts an argument of type (this) -> Result.
  • pkl.ref#Domain.renderReference() now accepts a Reference<this, Any>.
• This also a corner case with ReferenceTypeNode, module types, and type aliases that caused module types in the referent position to always be resolved to the module where the Reference type annotation is instead of where module is used.
• Pipes a Logger through to AstBuilder so warnings/traces can be printed from it.

For ease of review, this PR consists of two commits; the first is all implementation changes, the second includes regenerated pkl-doc test output.

Resolves #1612
Resolves #1712

[bioball]

I think this is getting close; did another pass.

One major comment here is: I think that we're missing a bunch of tests; there's a lot of positions in our grammar that can produce type nodes, which aren't tested.

Some of the ones that I can think of are:

• Object body param (foo { bar: this -> /* etc */ })
• Supertype (class Bar extends this {})
• Function literal type annotation ((arg: this) -> ...)
• For-generator variable
• Let expr variable
• Local object property new { local x: this = ... }
• Object method arguments (new { local function foo(bar: this): this = ... })
• Type cast expressions (foo as this)
• Constraint property type (foo: this(...))
• Function property type (foo: this -> this)
• Listing<this> (test lazy check and default value behavior)

[bioball]

Some minor nits and a test refactor, but otherwise LGTM!

Approving to unblock