Add is_remote_parent span flags to OTLP exported Spans and SpanLinks

[nikhilmantri0902]

Is your feature request related to a problem? Please describe.

After updating protobuf schema, we can set the is_remote_parent flag when exporting spans and span links with OTLP.

Describe the solution you'd like

Update OTLP exporter to fill the relevant bits in SpanFlags.

Describe alternatives you've considered

None

Additional context

Proto schema PR: open-telemetry/opentelemetry-proto#484
Go implementation: https://github.com/open-telemetry/opentelemetry-go/pull/5194/files
Python implementation: https://github.com/open-telemetry/opentelemetry-python/pull/3881/files

[nikhilmantri0902]

Shipping this feature will greatly help our product (signoz) in identifying and validating entrypoint spans.

[pichlermarc]

Yep, thanks for raising this issue - it will likely take some time for me to get to review the PR as my list is quite long, but I support this being added since it's a spec feature.