Draft:(resource/sem) Adding Datacenter Conventions.

[hdost]

• Would be good to unify potentially with "Cloud" conventions. To try to be a little more generic.

Relates to open-telemetry/semantic-conventions#1409, #1459

Fixes #

Changes

Please provide a brief description of the changes here.

For non-trivial changes, follow the change proposal process.

• Related issues #
• Related OTEP(s) #
• Links to the prototypes (when adding or changing features)
• CHANGELOG.md file updated for non-trivial changes
• spec-compliance-matrix.md updated if necessary

[dmathieu]

Semantic conventions have moved to https://github.com/open-telemetry/semantic-conventions/.
It looks like this is where this PR should be opened, not in this repo.