Modernization of the package

[Helveg]

Hi! I think you're the latest in a string of forks, hopefully you're still maintaining it? This PR overhauls the package with the following improvements:

Dependency Modernization

• Updated OTel dependencies for better compatibility.

  • Many OTel packages are experimental (0.x) but evolve quickly (current versions are around 0.203 while this package used 0.49).
  • Updated peer dependency ranges to <1 to reduce version conflicts.

Trace & Span Improvements

• Updated trace naming and span attributes to follow OpenTelemetry Semantic Conventions where applicable.
• Increased visibility and detail in spans throughout the NestJS instrumentation helpers.

README & User Guidance

• Added a minimal, clear introduction for users on how to instrument NestJS applications.
• Included a hint and link to official OTel docs for users unfamiliar with OpenTelemetry concepts.

Developer-Oriented Changes

• Updated package semantics to match modern OpenTelemetry conventions:

  • Renamed *Injector classes to *Instrumentation.
  • Improved naming consistency across helpers.

• Added InterceptorInstrumentation.

• Created a Tracer class token to replace the previous interface, making it easier to inject.

• Fixed a bug with useExisting providers not working properly.