[chore] Move Dynamodb attributes to the registry

[joaopgrassi]

Related to #407

Changes

Move AWS Dynamodb to the attributes registry

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.

[AlexanderWert]

The dynamoDB attributes namespace is inconsistent with the rest of all DBs (i.e. aws.dynamodb.* vs. db.dynamodb.*).
I'm wondering whether we should move these attributes now to the registry (and with that introduce the aws.dynamodb namespace in the registry) or wait until this resolved in the DB SemConv WG and move it then. I have no strong opinion though.

[joaopgrassi]

I will try to work on these AWS ones this week.

[joaopgrassi]

@AlexanderWert @trisch-me I applied the suggestions and this should be good for another review. Thanks!

[AlexanderWert]

LGTM