* Take advantage of coercing anonymous struct literals to struct types.
* Reworks Module to favor Zig source as the primary use case.
Breaks ZIR compilation, which will have to be restored in a future commit.
* Decl uses src_index rather then src, pointing to an AST Decl node
index, or ZIR Module Decl index, rather than a byte offset.
* ZIR instructions have an `analyzed_inst` field instead of Module
having a hash table.
* Module.Fn loses the `fn_type` field since it is redundant with
its `owner_decl` `TypedValue` type.
* Implement Type and Value copying. A ZIR Const instruction's TypedValue
is copied to the Decl arena during analysis, which allows freeing the
ZIR text instructions post-analysis.
* Don't flush the ELF file if there are compilation errors.
* Function return types allow arbitrarily complex expressions.
* AST->ZIR for function calls and return statements.
* add TypedValue.Managed which represents a Type, a Value, and some
kind of memory management strategy.
* introduce an analysis queue
* flesh out how incremental compilation works with respect to exports
* ir.text.Module is only capable of one error message during parsing
* link.zig no longer has a decl table map and instead has structs that
exist directly on ir.Module.Decl and ir.Module.Export
* implement primitive .text block allocation
* implement linker code for updating Decls and Exports
* implement null Type
Some supporting std lib changes:
* add std.ArrayList.appendSliceAssumeCapacity
* add std.fs.File.copyRange and copyRangeAll
* fix std.HashMap having modification safety on in ReleaseSmall builds
* add std.HashMap.putAssumeCapacityNoClobber
