Add support for missing environment variables to SDK

[owais]

State of tracing SDK env var support

• OTEL_RESOURCE_ATTRIBUTES
• OTEL_SERVICE_NAME
• OTEL_LOG_LEVEL Add support for OTEL_LOG_LEVEL env variable #1059
• OTEL_PROPAGATORS
• OTEL_TRACES_SAMPLER
• OTEL_TRACES_SAMPLER_ARG
• OTEL_BSP_SCHEDULE_DELAY
• OTEL_BSP_EXPORT_TIMEOUT
• OTEL_BSP_MAX_QUEUE_SIZE
• OTEL_BSP_MAX_EXPORT_BATCH_SIZE
• OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT Support global attribute limits #2051
• OTEL_ATTRIBUTE_COUNT_LIMIT Support OTEL_ATTRIBUTE_COUNT_LIMIT #2055
• OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT Add support for additional Span Limits #2044
• OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT
• OTEL_SPAN_EVENT_COUNT_LIMIT
• OTEL_SPAN_LINK_COUNT_LIMIT
• OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT Add support for additional Span Limits #2044
• OTEL_LINK_ATTRIBUTE_COUNT_LIMIT Add support for additional Span Limits #2044
• OTEL_EXPORTER_JAEGER_AGENT_HOST
• OTEL_EXPORTER_JAEGER_AGENT_PORT
• OTEL_EXPORTER_JAEGER_ENDPOINT
• OTEL_EXPORTER_JAEGER_TIMEOUT
• OTEL_EXPORTER_JAEGER_USER
• OTEL_EXPORTER_JAEGER_PASSWORD
• OTEL_EXPORTER_ZIPKIN_ENDPOINT
• OTEL_EXPORTER_ZIPKIN_TIMEOUT
• OTEL_TRACES_EXPORTER

[AndreasBergmeier6176]

Can you elaborate, why you think OTEL_SERVICE_NAME is implemented?
From my experience handling OTEL_SERVICE_NAME at least differs from opentelemetry-golang. The latter sets service.name when Environment Variable is present whereas here it seems like OTEL_SERVICE_NAME is used only in specific cases.
Also it seems like the following functionality is missing in Python: GoogleCloudPlatform/opentelemetry-operations-go@227b0dc