OTEL schema files should be in a single repo

[chalin]

OTEL schema files are duplicated across this repo and opentelemetry-specification. Here's some more context for this issue:

• Publish OpenTelemetry Schema File 1.6.1 #695 (comment):

  ... is there a problem if the content of these two directories drift apart?

  • https://github.com/open-telemetry/opentelemetry.io/tree/main/static/schemas
  • https://github.com/open-telemetry/opentelemetry-specification/tree/main/schemas

  
  Should 1.6.0 be deleted from `opentelemetry-specification/schemas` too, "as if it never happened"?

• Publish OpenTelemetry Schema File 1.6.1 #695 (comment)

  Good catch. Yes, it should be deleted.

  The content of the directories should be in sync and I plan to add an action that syncs the content automatically.

The schema files should reside in a single repo (probably opentelemetry-specification). File copying across repos leads problems like the above, as well as those mentioned in #661, even if there is an action to sync (one way):

Disadvantages of file mirroring and copying:

• We loose true edit/blame history
• There's the risk of edits being done in the wrong place (since files are present in two repos)
• There's potential confusion of where to open issues (again, since files are present in two repos)

In this case, I'd like to suggest bringing opentelemetry-specification/schemas into this repo via a submodule.

[austinlparker]

Yeah, I concur that this should be a submodule. Could we continue to have push-button automation from the spec side in order to do the submodule update if that's how they're doing it now?