Prohibit usage of retired names in semantic conventions (#2191)

* Prohibit usage of retired names in semantic conventions

This change adds a prohibition clause that requires that no old
metric or attribute name is used for a new attribute.

This is important to ensure reversibility of schema transformation
(converting from a new version to an old version of schema).

Without this restriction the following is possible:

Schema version 1. Attribute A exists.
Schema version 2. Attribute A is renamed to B. Appropriate schema file is created.
Schema version 3. Attribute A is introduced (a completely different new attribute).

Now attempting to go from Version 3 to version 1 is impossible since it requires
renaming B to A (for the change in version 2), but a different attribute A already exists.

* Fix based on comments

* Add changelog entry

Co-authored-by: Carlos Alberto Cortez <[email protected]>

specification/common/attribute-naming.md

@@ -8,6 +8,7 @@
 <!-- toc -->
 
 - [Name Pluralization guidelines](#name-pluralization-guidelines)
+- [Name Reuse Prohibition](#name-reuse-prohibition)
 - [Recommendations for OpenTelemetry Authors](#recommendations-for-opentelemetry-authors)
 - [Recommendations for Application Developers](#recommendations-for-application-developers)
 - [otel.* Namespace](#otel-namespace)
@@ -67,6 +68,15 @@ Names SHOULD follow these rules:
   [Metric Name Pluralization Guidelines](../metrics/semantic_conventions/README.md#pluralization)
   SHOULD be followed for the attribute name.
 
+## Name Reuse Prohibition
+
+A new attribute MUST NOT be added with the same name as an attribute that
+existed in the past but was renamed (with a corresponding schema file).
+
+When introducing a new attribute name check all existing schema files to make
+sure the name does not appear as a key of any "rename_attributes" section (keys
+denote old attribute names in rename operations).
+
 ## Recommendations for OpenTelemetry Authors
 
 - All names that are part of OpenTelemetry semantic conventions SHOULD be part