Correctly parse `tags` from remote trace sampling rules and improves
overall rule parsing reliability through stricter validation and clearer
error reporting.

Changes:
  - Add support for `tags` in trace sampling rules.
  - Improve validation with explicit type checks and more descriptive
    error messages.
  - Update catch-all rule handling to replace an existing one instead of
    always prepending, ensuring consistent rule ordering.
  - Extended system test request handler to support `span_tags` from
    incoming requests.

[APMAPI-863]
[APMAPI-866]