Add target filtering for logs

[ravakella-ms]

Adding a target_filter attribute for LogExportTargets struct. This will help users attach a target to their logs and make sure only a subset of the logs are going to be exported to the Otel collector

Unrelated to the main feature, there is a make test failure in mocks.rs. The [clippy::result_large_err] lint warns when the [Err] variant of a Result<T, E> type is very large (in this case, 176 bytes). This can be problematic because:

• Memory Usage: Result<T, E> is stored as a tagged union, so it takes up space equal to the larger of T or E plus some overhead for the discriminant tag.
• Performance: Large error types can impact performance during:
  Stack allocation/deallocation, Moving/copying the Result around, etc

Why is tonic::Status Large?
The tonic::Status type is large because it contains:
Error code, Error message (String), Error details, Metadata, Source information. All of this adds up to 176+ bytes.
But since this code is:

• Test/mock code (not production)
• A simple interceptor that rarely fails
• Following the tonic interceptor API signature
  The #[allow(clippy::result_large_err)] is reasonable here because:
• We can't easily change the API (it's defined by tonic)
• The performance impact is minimal in tests
• Boxing the error would add unnecessary heap allocation for test code