Request more fine-grained control for remote sampling

[garrettlish]

Problem Statement

The PerOperationSampler provides operation-level customized sampling probabilities but lacks support for more fine-grained control, such as adjusting sampling probabilities based on specific tag key-value pairs (see sampling.proto).

For instance, in a real-world scenario, we might want to enforce sampling for a particular user session by customizing sampling probabilities based on specific tag key-value pairs.

Proposed Solution

Introduce a tag key-value pair in OperationSamplingStrategy to enable fine-grained control for remote sampling.

[dmathieu]

cc @yurishkuro as codeowner of the jaegerremote sampler.