cm: Use public type for errorContext wasm functions

[lxfontes]

wadge ( Test Harness generator ) scans all generated code and no longer works with cm package version 2.x.

code generated via wit-bindgen-go uses Public Types for wasmimport/export functions.
The newly introduced ErrorContext in cm uses a private type ( errorContext ), making it impossible to shim it with go:linkname.

# github.com/wasmCloud/go/examples/component/http-server_test [github.com/wasmCloud/go/examples/component/http-server.test]
./bindings.wadge_test.go:24:78: name errorContext not exported by package cm
./bindings.wadge_test.go:44:70: name errorContext not exported by package cm
FAIL	github.com/wasmCloud/go/examples/component/http-server [build failed]

what wadge generates after parsing wit generated code: