docs: Update Bedrock documentation to show streaming example

[Amnah199]

Is your feature request related to a problem? Please describe.
The BedrockGenerator now supports streaming_callback, similar to the OpenAIGenerator. After its release, it would be beneficial to include an example of 'Streaming' in the documentation to demonstrate its usage.

Describe the solution you'd like
Add a separate example code for streaming, similar to the example provided for the OpenAIGenerator in the documentation:
OpenAIGenerator Example.

Describe alternatives you've considered
NA
Additional context
NA

[dfokina]

I attempted to make the information about streaming support more visible to users without manually rewriting examples for each component page:

• Added a column to the Generators overview table.
• Explained streaming support in Choosing the Right Generator guide with a generic example.
• Added a reusable snippet called "Streaming" to the pages of Generators that support streaming.

This way, all three pages are somewhat interconnected, so users should be able to easily find this information.

@Amnah199 @julian-risch please take a look if this makes sense before I close this :)