add MetalVectorStore + MetalReader (#1784)

* init llama index metal vector store

* fix comment

* fix comments

* fix import

* rm comment

* update to incl filters

* add MetalReader

* add metalreader import

* adj comments

* add deletion

* retrieve from data

* swap dist to similarity

* use data

* make idmap optional

* add metal example

* rm config_dict + from_dict

* update to use embedding rather than pass in text

* fix del

* adjust node interface

* adjust callouts.

* rm id_to_text_map

* fi node

* actually, lets leave it

* uno mas

* rm id mapping again

* add