feat(core): enhance logging with request context information

[tanujs108]

Description

This PR enhances APISIX's core logging functionality by automatically adding request context information to all log messages, significantly improving debugging and operational visibility.

• Add request_id, route_id, and route_name to all log messages
• Implement get_request_context() to extract context from nginx and APISIX
• Implement enhance_log_message() to prepend context to log output
• Use format: [request_id=xxx,route_id=xxx,route_name=xxx] message
• Minimal performance impact with safe extraction using pcall
• Improves debugging and request tracing capabilities

Problem Solved:

• Standard APISIX logs provide limited context for request tracing
• Debugging request-specific issues requires manual correlation across multiple log sources
• Route-specific problems are hard to identify in high-traffic environments

Changes Made:

1. get_request_context() function extracts:

   • request_id from ngx.var.request_id (nginx-generated unique identifier)
   • route_id and route_name from ngx.ctx.api_ctx (APISIX context)
   • Uses pcall for safe extraction with graceful fallback

2. enhance_log_message() function:

   • Automatically prepends context to all log messages
   • Only adds context when available (zero overhead when context missing)

Which issue(s) this PR fixes:

Fixes #

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[Baoyuantop]

Hi @tanujs108, for this scenario, our preferred solution is to include the request ID in the error log and correlate it with the access log. This provides the full context of the request. In fact, the underlying library already supports this capability, and we are considering adding this feature in future versions of APISIX.