Implement merging semver-compatible interfaces in imports

[alexcrichton]

This commit is the first half and the meat of the implementation of #1774 where, by default, WIT processing tools will now merge world imports when possible based on semver versions. The precise shape of how this is done has gone through a few iterations and this is the end result I've ended up settling on. This should handle all the various cases we're interested in and continue to produce valid worlds within a Resolve (with the help of elaborate_world added in #1800). CLI tooling has been updated with flags to configure this behavior but the behavior is now enabled by default.

Closes #1774

[alexcrichton]

This is a draft PR at this time because changes are needed to wit-component to enable this to actually work. While interfaces are correctly merged at the WIT level they're not yet hooked up to core wasm that imports the "old" version. Once #1810 lands that connection will be much easier to implement and I plan on adding a follow-up with test cases here as well.

[alexcrichton]

Ok and now with #1810 landed I was hoping this was ready to go. I realized though I should also test with the original .NET component that @dicej had to ensure this works. That's uncovering some more issues so this isn't actually quite ready yet.

[alexcrichton]

Ok Joel you gave me a module.wasm awhile ago which raised this issue initially and I now get:

$ cargo run component embed --world proxy ../wasi-http-0.2.0/wit ./module.wasm | \
    cargo run component embed --world imports ../wasi-http-0.2.1/wit | \
    cargo run component new --adapt ./wasi_snapshot_preview1.reactor.wasm | \
    tee composed.wasm | \
    cargo run validate

all passes. A simple wasmtime serve of the component works as well and I also see:

$ wasm-tools component wit ./composed.wasm
package root:component;

world root {
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:io/[email protected];
  import wasi:io/[email protected];
  import wasi:io/[email protected];
  import wasi:clocks/[email protected];
  import wasi:filesystem/[email protected];
  import wasi:filesystem/[email protected];
  import wasi:sockets/[email protected];
  import wasi:clocks/[email protected];
  import wasi:sockets/[email protected];
  import wasi:random/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:cli/[email protected];
  import wasi:http/[email protected];

  export wasi:http/[email protected];

}
...

where notably was:io/poll is only present at 0.2.1 and other interfaces are deduplicated.