wasmtime-cli: component run's --invoke uses ItemName for search

[pchickey]

Forwards-compatible improvements to wasmtime run --invoke on components:

• Now uses wit_parser::ItemName as the parser for the function name in the wave expression (new in wasm-tools 251), look up via ExportLookup, both changes to make this possible introduced by wasmtime: impl ExportLookup for wit_parser::ItemName #13505
• Previously, when the search for a function in all of the exported instances turned up multiple candidates, failed with a FIXME in the error message. Now, the error message suggests the set of qualified names to select from instead. Example error from integration tests:

Multiple instances contained funcs named `run`, retry with a more specific name: `wasi:cli/run.run@0.2.0`, `some:other/one.run`