Feat/bedrock converse partial system prompt cache

[gringParis]

Description

Allow system prompt caching with cache point mechanism as discussed here #19737 (comment)

I also noticed that using the system_prompt_caching parameter from that merged pull request raised an error by bedrock converse api. .

The system_prompt_caching parameter from BedrockConverse is preserved and can still be used.

Fixes # (issue)
fixes this issue

New Package? Its not a new package

Did I fill in the tool.llamahub section in the pyproject.toml and provide a detailed README.md for my new integration or package?

• Yes
• No

Version Bump?

Did I bump the version in the pyproject.toml file of the package I am updating? (Except for the llama-index-core package)

• Yes
• No

Type of Change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• [] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Your pull-request will likely not be merged unless it is covered by some form of impactful unit testing.

• I added new unit tests to cover this change
• I believe this change is already covered by existing unit tests

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added Google Colab support for the newly added notebooks.
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran uv run make format; uv run make lint to appease the lint gods

[gringParis]

@logan-markewich @mattref
This is a follow up of my comment on that pr