Add `component::Linker::instantiate_concurrent`

Frist proposed in https://github.com/bytecodealliance/wasmtime/pull/13706, although the implementation there wasn't sound, but the idea is that the same way `Func::call_concurrent` can be used it should be possible to concurrently instantiate instances. This implementation is going to touch on https://github.com/bytecodealliance/wasmtime/issues/11870 and https://github.com/bytecodealliance/wasmtime/issues/11869, however. This may also touch on the spec as this is likely an area where we diverge by accident.

Start by reviewing the proposed implementation in pull request 13706, then read issues 11870 and 11869 alongside the existing Func::call_concurrent behavior. Determine sound concurrent-instantiation semantics and whether the WebAssembly specification requires changes; done means an agreed design that resolves these compatibility and safety questions.

Written by the indexing model from the issue text.