cleanup: simplify main module resolution

[zshipko]

This PR simplifies the resolution of the main module when multiple modules are provided. Before we would try to look at the path/URL when the wasm was coming from disk or via HTTP, now any module missing a name will be used as main. This is much nicer and more consistent since this is what was being done when no filename was available (i.e. raw data modules). It also make sense because non-main modules will need to be named for the functions to be linked correctly.

[nilslice]

does this impact anything in the go or js SDKs? cc/ @mhmd-azeez

(I mean in the sense that we need to make a similar change in those implementations)

[chrisdickinson]

@nilslice While the JS SDK supports loading multiple modules, it doesn't currently implement linking (extism/js-sdk#29). (I'd like to get that done as part of the post-beta/pre-release polish, though.) (Edit: In addition, we'll want to implement proper name derivation that matches libextism. Right now it guesses absent names based on hash or index & doesn't have a concept of a main.)

[nilslice]

@chrisdickinson ok great, thanks! still probably worth a check on the Go SDK, but if I recall there is some existing special checking done to handle this.. just want to be sure we are consistent

[zshipko]

Good point, I can take a look at the go-sdk too and if I can't figure it out will just open an issue.

[chrisdickinson]

LGTM! This is a nice refinement. The only open question I had was whether the kernel counted towards our minimum module count check. (Edit: I was misreading the module count check, apologies! This looks great.)

[zshipko]

Merging this now and opened a PR to update the go-sdk: extism/go-sdk#42