config: add support for configuring custom log/span processors

[vigneshshanmugam]

Problem Statement

Configuring custom span/log processors via the config doesn't currently work, This is required for enhancing the telemetry for the OTel collector

We can also extend the config to add support for the metric processors once the spec open-telemetry/opentelemetry-specification#4298 lands.

Proposed Solution

Use the processors from the configuration in addition to the built in simple/batch processors and set the processors based on the order they are configured. Follow the defined spec - https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk.md

Alternatives

None

Additional Context

See the discussion - open-telemetry/opentelemetry-collector#12316