fixing default service name

[brettmc]

default service name should contain runtime name if available: java just appends ":java" so I did the same.
ref: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/semantic_conventions/README.md#service

[codecov]

Codecov Report

Merging #887 (29631d4) into main (587bc5a) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #887   +/-   ##
=========================================
  Coverage     81.56%   81.56%           
  Complexity     2008     2008           
=========================================
  Files           264      264           
  Lines          5219     5219           
=========================================
  Hits           4257     4257           
  Misses          962      962           

Flag	Coverage Δ
7.4	81.05% <ø> (ø)
8.0	81.55% <ø> (ø)
8.1	81.69% <ø> (ø)

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Impacted Files	Coverage Δ
src/SDK/Resource/Detectors/SdkProvided.php	100.00% <ø> (ø)

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[pdelewski]

default service name should contain runtime name if available: java just appends ":java" so I did the same.

Interesting, I was thinking that this requires something more sophisticated :)