[tubopack] migrate rcstr! to use scattered collect (#94498)
### What?
Adopt
`[scattered_collect`](https://docs.rs/scattered-collect/latest/scattered_collect/)
for collecting static rcstr values.
### Why?
Built by our good friend @mmastrac to solve some of our problems.
Replaces inventory with a simpler linker driver approach.
Basically inventory works using constructor functions to build a linked
list, then iterating follows the list. `scattered_collect` on the
otherhand uses a linker section for the data, so it all gets moved to a
dedicated part of the binary and bingo, a slice!. This means we don't
need `init` time logic.
This is preparation for migrating other uses of `inventory` just to
prove it out. Which was a good idea because we found and fixed a bug!
See
https://github.com/mmastrac/linktime/releases/tag/link-section-0.18.2
## Wasm
scatter_collect supports wasm, but requires us to register a 'section
reader' function with the runtime, see
https://docs.rs/link-section/latest/link_section/#wasm. The instructions
are staightforward but a little tricky since we rely on `wasm-bindgen`
to constrct the `Wasm.Module` instance and it is encapsulated. So to
'inject' that function we would need to patch some of the bootstrapping.
Given that this registry is only an optimization for deserialization
which never happens in a wasm build i just flagged it all off.
