* 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 <calberto.cortez@gmail.com>
Josh Suereth