Yaml schema: unify semconv identity property

[lmolkova]

• attributes have id
• events have name
• metrics have metric_name
• resource have name

resources and spans don't have identity except the group-id.

We should consider unifying a property that describes a full name of a thing, especially if it's meaningful outside of semconv repo, e.g. for code generation and instrumentations.

[jsuereth]

resources now have name, which denote a "TYPE" identity, awkwardly.