Disambiguate attribute deprecation

[lmolkova]

There are currently two ways to deprecate at attribute:

1. By setting stability to deprecated

   - id: status_code
     brief: 'Deprecated, use `http.response.status_code` instead.'
     stability: deprecated
     ....

2. By providing deprecated: description property

   - id: status_code
     deprecated: "use `http.response.status_code` instead."

The first approach is problematic: once attribute is deprecated it's no longer possible to know what was the stability at deprecation time.
It's problematic for code generation:

• I want to separate experimental and stable attributes into different artifacts (or packages) based on stability level - I no longer know where to put deprecated ones (where they used to be)
• I want to drop deprecated attributes that were experimental at deprecation time and only keep ones that were stable at deprecation time - I'm not able to do it.

Related to #551

[lmolkova]

Proposal:

• only use the 2nd way in semconv defined here
• change build-tools to remove stability: deprecated option
• use deprecated: str property in jinja templates to check deprecation status (Support codegen by namespace build-tools#243 introduces a helper method)

[arminru]

+1 on your proposal, sounds like the ideal solution to me

cc @open-telemetry/build-tools-approvers

[lmolkova]

reopening since open-telemetry/build-tools#244 is not merged

[joaopgrassi]

I merged open-telemetry/build-tools#244 now.