UDPExporter should be useable when Application Signals is disabled on Lambda

[jj22ee]

Issue #, if available:
Currently, if AppSignals is disabled, UDP Span Exporter not usable in Lambda.

According to this comment, the correct logic should be:

If isLambdaEnvironment is true, we will default to exporting OTel spans via udp_exporter, regardless of whether AppSignals is true or false.

Currently, this is not respected because when AppSignals is disabled, ADOT's otel config cannot use the UDPExporter

• Currently, the only difference between the AppSignals enabled and AppSignals disabled configurations is that in the "disabled" case, ADOT leaves the Span Exporter/Processor and textMapPropagator initialization work to the OTel JS SDK. Only in AppSignals enabled scenario, the configured UDPExporter is accessible.

Description of changes:
Update configure() to not depend on AppSignalsEnabled flag (always use the Span Exporter/Processor and textMapPropagator configurations made from the ADOT configurator)

• Similarly to Python, always use the ADOT configured Span Exporter/Processor, which is already configured based on the AppSignalsEnabled flag
• textMapPropagator configuration is still using upstream's configuration (includes the XRay Propagator)

Testing:

• Add Unit Test
• Test that spans are exported in Lambda when AppSignals is disabled

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