Rename examples so the example names represent core capabilities demonstrated by the example #398

Use cases, pain points, and background
Not all users will know that things like "simple_weather" is of interest because it showcases single-step tool calling. The same goes for "instruction_following" and "stateful_counter."

Description:
Rename resource server examples so their names are associated with their core capabilities.
For example "simple_weather" -> "example_single_tool_call"
and "stateful_counter" -> "example_session_state_mgmt"

Design:

• Modify README in Github
• Modify associated docs.nvidia.com pages and resource server examples in places like:
  • Resource server in core abstractions
  • Setup page that uses example resource server
• Modify actual resource servers and their respective READMEs across Github

Out of scope:

• READMEs for each individual resource server should be improved as per simple_weather example README is empty #227

Acceptance Criteria:

• Update Github root README
• Update NVIDIA docs so that all examples that use these resource servers still work
• Modify each individual Github resource server README