[feature] Build tools/schema should define code-friendly attribute/metric/event/etc names

[jsuereth]

See open-telemetry/semantic-conventions#1118 for context

[jsuereth]

We are no longer changing how constants are named. We will either be dropping deprecated names or keeping both with different names in some way.

[lmolkova]

Based on the conclusion in open-telemetry/semantic-conventions#1118 (comment), we need to be able to resolve codegen conflicts at semconv definition time.

E.g.:

• messaging.client_id should be marked as dropped in code, see for the details messaging.client_id -> messaging.client.id rename causes issues with code generation semantic-conventions#1031 (comment). The same option could be used for other low-usage attributes
• if we want to preserve an old attribute in the code, we'd need to be able to define a code-friendly constant name in yaml
• the same mechanism could be used to support a wider range of characters (see Attribute names: unicode on OTLP, only [a-z0-9._] in OTel semcov semantic-conventions#1124)

Some ideas

1. dropping old

   attributes:
     - id: foo.bar_baz
       deprecated: "Use `foo.bar.baz` instead"
       code_friendly_name: none # new, optional property, defaults to snake_case(id) 

2. preserving old and giving new attribute new code const name

   attributes:
     - id: foo.bar_baz
       deprecated: "Use `foo.bar.baz` instead"
   
     - id: foo.bar.baz
       code_friendly_name: foo_bar_baz2

3. Defining code-friendly name for not supported characters

     - id: pprof::foo.bar
       code_friendly_name: pprof_foo_bar

[lmolkova]

closing in favor of open-telemetry/semantic-conventions#1462