Eglot: filter by prefix in narrow-scope eglot-code-actions

Eglot: filter by prefix in narrow-scope eglot-code-actions

Github-reference: https://github.com/joaotavora/eglot/issues/847

Servers like typescript-language-server, when asked for {"only" :
"source.organizeImports"}, return actions with the
"source.organizeImports.ts" kind.  Eglot rejected these actions, but
according to the spec:

  Kinds are a hierarchical list of identifiers separated by `.` [...]
  The set of kinds is open.

So I guess we can use string-prefix-p

* lisp/progmodes/eglot.el (eglot-code-actions): Use string-prefix-p.