user lowercase for event names

[cijothomas]

https://github.com/open-telemetry/otel-arrow/blob/main/rust/otap-dataflow/docs/telemetry/events-guide.md#event-naming

Moving to lowercase. We are not fully following the guided name yet. Will tackle that one module at a time in follow ups.

[codecov]

Codecov Report

❌ Patch coverage is 44.44444% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.40%. Comparing base (c68e70e) to head (c07dcd0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1816      +/-   ##
==========================================
- Coverage   84.40%   84.40%   -0.01%     
==========================================
  Files         496      496              
  Lines      145393   145393              
==========================================
- Hits       122719   122718       -1     
- Misses      22140    22141       +1     
  Partials      534      534              

Components	Coverage Δ
otap-dataflow	85.68% <44.44%> (-0.01%)	⬇️
query_abstraction	80.61% <ø> (ø)
query_engine	90.52% <ø> (ø)
syslog_cef_receivers	∅ <ø> (∅)
otel-arrow-go	53.50% <ø> (ø)
quiver	90.66% <ø> (ø)

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