Named WASI contexts must share one ResourceTable, but this isn't documented #14857

When using named imports with wasmtime-wasi (add_named_to_linker), the per-name contexts have to share the default ResourceTable, but nothing says so, and WasiHttpNamedView's docs suggest the opposite ("need not be unique").

Named implementations push resources into the named view's table, while the plain interfaces that consume them (e.g. wasi:io/streams in p2) read the default table. With a table per id, reading a labelled wasi:cli/stdin returned the default context's input in a test, and p3 http fails with failed to delete request from table.

At minimum this needs documenting on WasiNamedView/WasiHttpNamedView. An API that returns the per-id context and the shared table separately would make it impossible to get wrong.