fix(instrumentation-runtime-node): fix .isEnabled()

[trentm]

This instrumentation overrides the enable() and disable() methods. However,
it was not calling super for those, so the private '_enabled' state on
the super class was not getting updated, which broke 'instr.isEnable()'.
It would always return false.

example showing isEnabled() not working

> var mod = require('@opentelemetry/instrumentation-runtime-node')
undefined
> var instr = new mod.RuntimeNodeInstrumentation()
undefined
> instr.isEnabled()
false
> instr.enable()
undefined
> instr.isEnabled()
false

That last .isEnabled() result should be true.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.05%. Comparing base (e9987a7) to head (1dcfe4e).

Files with missing lines	Patch %	Lines
...nstrumentation-runtime-node/src/instrumentation.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2946      +/-   ##
==========================================
- Coverage   89.06%   89.05%   -0.01%     
==========================================
  Files         188      188              
  Lines        9219     9221       +2     
  Branches     1900     1900              
==========================================
+ Hits         8211     8212       +1     
- Misses       1008     1009       +1     

Files with missing lines	Coverage Δ
...nstrumentation-runtime-node/src/instrumentation.ts	87.09% <50.00%> (-2.56%)	⬇️

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[david-luna]

Hopefully codecov will be improved when #2866. is merged.