Co-authored-by: James Bunch <fallwith@gmail.com>

Previously, trace_id, span_id, and trace_flags were assigned based on
the OpenTelemetry::Trace.current_span's SpanContext. The specification
requires a context be accepted as an argument on emit.

If no context is provided, OpenTelemetry::Context.current will be used.

If there isn't a current span on OpenTelemetry::Context.current
trace_id, span_id, and trace_flags will be nil unless they are passed
as arguments.

Also, remaining #emit methods are renamed to #on_emit.

This code was leftover and should have been removed.
Now, the specfic `trace_id`, `span_id`, and `trace_flags`
attributes are used instead.

…lemetry-ruby into logs-sdk-log-record