Inconsistent console exporter behavior/documentation

[smaddock]

Is your feature request related to a problem?
Not really a problem, but an observation.

Code discrepancies:

• OpenTelemetry\SDK\Logs\Exporter\ConsoleExporter depends on being created by ConsoleExporterFactory to create the appropriate stream transport, otherwise it's not actually exporting to the consol
• OpenTelemetry\SDK\Metrics\MetricExporter\ConsoleMetricExporter uses echo for output (the only time echo is used anywhere in the SDK)
• OpenTelemetry\SDK\Trace\SpanExporter\ConsoleSpanExporter depends on SpanExporterFactoryInterface in the same manner as the Log exporter

Documentation discrepancies:

Referencing this otel.io page:

• Under "Instrumentation setup>Initialize the SDK" the example instrumentation.php creates each exporter by configuring the stream transport directly
• Under "Traces>Span Processor" the ConsoleSpanExporterFactory is used
• Under "Metrics>Setup" the ConsoleMetricExporterFactory is used
• Under "Logs>Setup" the stream transport is configured directly

Describe the solution you'd like

• Update ConsoleMetricExporter to use a transport instead of echo
• Update all three exporters to have a default stream transport targeting php://stdout so they are functionally "console" exporters even without the factory
• Remove the (then redundant) default transport from the factories
• Update the documentation to use the console exporter factory in all instances

Describe alternatives you've considered
Checked for any related issues, did not see any.

Additional context
None.

[smaddock]

I'm hoping to submit a PR for this in the next couple weeks, but it should be an easy one for a first issue or if someone is itching to submit one.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.