Use semantic convention attribute for cloud region for botocore API calls

[SrdjanLL]

Description

This change is a result of the conversation on semantic conventions and the correct use of the cloud region attribute (see open-telemetry/semantic-conventions#2142 for details). This PR depends on the semantic conventions update to expand the definition of cloud.region attribute (PR).

Changes made:

• Update botocore instrumentation to use semantic convention attribute for cloud region
  • Region will no longer be captured as aws.region attribute.
• Update tests to reflect this change.

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
  • This change removes aws.region from the span attributes in favour of cloud.region which may affect existing functionality.

How Has This Been Tested?

• Updated unit tests that assert the span attributes.
• Smoke-tested using the bedrock-runtime examples provided alongside the instrumentation library.

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No, but it does require semantic conventions change: Expand the intended use of the cloud.region attribute semantic-conventions#2238.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[xrmx]

Sem conv changes merged so we can merge this too