Clean up OTEL_EXPORTER_OTLP_(*_)ENDPOINT environment variables

[puckpuck]

Per the specification for the OTEL_EXPORTER_OTLP_ENDPOINT and we should not set the path when used (i.e.: /v1/traces). If setting the path, this needs to be done with the telemetry-specific variable i.e.: OTEL_EXPORTER_OTLP_TRACES_ENDPOINT. Some SDKs or use cases require the use of telemetry-specific variables. When that is the case, the generic one should not be included in that service's container.

The telemetry-specific environment variables are used in nearly all services, but the default value specified in the .env file is without the path specified, violating the specification. A few services do override the default and specify the path. We should make the path part of the defaults in .env.

The frontend demo component (perhaps others) specifies both the telemetry-specific and the non-telemetry-specific environment variables. This should be cleaned up as well.