Create a registry for loggers to make sure a logger with an identical
name and version is created only once and reused

When OTLP logs exporter not installed, rescue the error, emit a message
and set the exporter to nil.

…pentelemetry-ruby into logs-configuration-patch

Previously, a no-op Logger was returned when LoggerProvider#logger was
called after the provider was stopped.

Now, when the provider is stopped, the on_emit method will return early
and not emit any log records.

This more closely follows the behavior in the TracerProvider.