Update nginx instrumentation

[seemk]

• Works with latest nginx versions.
• Removed toml configuration, everything is configurable from the nginx configuration and/or environment variables now.
• Replaced gRPC with OTLP over HTTP - reduces the amount of dependencies needed to build.
• Updated the buids and CI to test and build binaries on different Linux distros.
• New nginx directives due to the removal of toml configuration: opentelemetry_service_name, opentelemetry_span_processor, opentelemetry_otlp_traces_endpoint, opentelemetry_traces_sampler, opentelemetry_traces_sampler_ratio, opentelemetry_bsp_schedule_delay_millis, opentelemetry_bsp_max_export_batch_size, opentelemetry_bsp_max_queue_size.

[seemk]

@tobiasstadler Not sure if you're still around, but will need an approval to merge it.

@lalitb If no approver is around, can I have an approval? Going to do additional updates (and go over the open issues).