feat: reorganize libraries (#3347)

- rename `IbcVersionId` to `IbcSpecId` as this type no longer represents
an IBC *version*, but rather the entire specification
- clean up `ibc-solidity`, removing unused definitions and moving some
that are only used in one place into said place where they're used. this
crate now only defines the IBC stack itself, so the `ibc` module was
also inlined
- split IBC spec definitions out of `voyager-message` into their own
crates
- these crates define the interface of the individual IBC interfaces;
there are still some rough edges but this is a good start
- remove `ics24` module from `unionlabs` and move those store path
definitions into the relevant IBC spec libraries
  - TODO: move `unionlabs::id` as well
- `union-ibc` now depends on `voyager-core`. i'm not super happy about
this, but it's fine for now - i'm still working on the library design
for the IBC specs, but i will likely split them further such that
`union-ibc` can only depend on the parts it needs.