Refactor analyzer name resolution (resolve_name/NamedThing)

[sbillig]

This consolidates all named things into a NamedThing hierarchy, and name resolution into a single resolve_name chain (block -> fn -> contract -> module), along with some related refactoring. This is mostly groundwork for the module system, and moves us in the direction of representing built-ins as declarative structures that are analyzed using general-purpose code that will work for things defined in fe (when the language is sufficiently powerful).

Notably, checking of generic type parameters for the built-in generic types String and Map is now handled in a general-purpose apply_generic_type_args function which will work for generic types defined in fe, rather than special-case code.

Note that I've postponed the module-level fn definition support functionality for now. I'll do that in a separate PR.

To-Do

• Add entry to the release notes (may forgo for trivial changes)

• Clean up commit history

[codecov-commenter]

Codecov Report

Merging #555 (c488fd0) into master (262a20a) will decrease coverage by 1.29%.
The diff coverage is 78.69%.

@@            Coverage Diff             @@
##           master     #555      +/-   ##
==========================================
- Coverage   87.49%   86.19%   -1.30%     
==========================================
  Files          88       87       -1     
  Lines        6095     6369     +274     
==========================================
+ Hits         5333     5490     +157     
- Misses        762      879     +117     

Impacted Files	Coverage Δ
crates/analyzer/src/traversal/functions.rs	93.22% <ø> (ø)
crates/analyzer/src/context.rs	78.26% <56.52%> (-7.16%)	⬇️
crates/analyzer/src/db/queries/contracts.rs	94.32% <61.53%> (-3.44%)	⬇️
crates/analyzer/src/namespace/items.rs	79.57% <64.03%> (-10.29%)	⬇️
crates/analyzer/src/namespace/types.rs	71.12% <70.96%> (-2.40%)	⬇️
crates/parser/src/ast.rs	78.17% <75.00%> (+0.26%)	⬆️
crates/analyzer/src/namespace/scopes.rs	72.61% <76.82%> (-8.91%)	⬇️
crates/lowering/src/mappers/module.rs	77.35% <78.26%> (-7.43%)	⬇️
crates/analyzer/src/traversal/expressions.rs	88.47% <81.25%> (-2.58%)	⬇️
crates/analyzer/src/traversal/types.rs	85.56% <85.36%> (-8.80%)	⬇️
... and 13 more

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[g-r-a-n-t]

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