feat(bedrock): add docs for SystemContentBlock caching approach

[dbschmigelski]

Description

This is the followup to feat(models): add SystemContentBlock support for provider-agnostic caching strands-agents/sdk-python#1112. It includes documentation to describe the new approach.

After strands-agents/sdk-python#1141 is merged, we will update the LiteLLM section. Then after that as we begin progressing on [FEATURE] Prompt caching support for all models strands-agents/sdk-python#1140 we will update docs to provide a general caching section

Type of Change

• Content update/revision

Motivation and Context

strands-agents/sdk-python#1112

Areas Affected

http://127.0.0.1:8000/user-guide/concepts/model-providers/amazon-bedrock/#caching

Screenshots

Checklist

• I have read the CONTRIBUTING document
• My changes follow the project's documentation style
• I have tested the documentation locally using mkdocs serve
• Links in the documentation are valid and working
• Images/diagrams are properly sized and formatted
• All new and existing tests pass

Additional Notes

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.