Package hashing was not properly handling multimethods. In particular, it was removing
any functions that had decorators from the output, so we'd miss things like
`@run_after("install")`, etc.
There were also problems with handling multiple `@when`'s in a single file, and with
handling `@when` functions that *had* to be evaluated dynamically.
- [x] Rework static `@when` resolution for package hash
- [x] Ensure that functions with decorators are not removed from output
- [x] Add tests for many different @when scenarios (multiple @when's,
combining with other decorators, default/no default, etc.)
Co-authored-by: Danny McClanahan <1305167+cosmicexplorer@users.noreply.github.com>
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