Extend GenAI system to support IBM Watsonx AI and AWS Bedrock

[gyliu513]

Added IBM Watsonx AI and AWS Bedrock to the list of possible values that the gen_ai.system attribute can take.

Changes

The following are added:

• IBM Watsonx AI
• AWS Bedrock

Please provide a brief description of the changes here.

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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.