Conditions to rename attributes, metrics, and events in stable semconv

[lmolkova]

Currently, spec allows to rename things:

opentelemetry-specification/specification/versioning-and-stability.md

Lines 233 to 239 in 4229197

	Changes to semantic conventions in this specification are allowed, provided that
	the changes can be described by schema files. The following changes can be
	currently described and are allowed:
	- Renaming of span, metric, log and resource attributes.
	- Renaming of metrics.
	- Renaming of span events.

After attribute/semantic convention reaches stability, there is very little benefit in renaming attributes, metrics, or events.

Even though schema transformation can hypothetically patch old data and align it with newer version, it would not help custom tooling: custom queries, alerts, and dashboards that are built on top of old schema.

Given that risks and complexity are high and benefits are low, should we keep allowing renames? If so, we should define the bar and clarify that rename is an exceptional thing.

[trask]

(related: #3380)