Introduce a LabeledStatsdClient API; no callers yet.
Include three config options:
- statsd_label_mode, which specifies which label format to use
- statsd_emit_legacy, which dictates whether to emit old-style
metrics dotted metrics
- statsd_user_label_<name> = <value>, which supports user defined
labels in restricted ASCII characters
Co-Authored-By: yanxiao@nvidia.com
Co-Authored-By: alistairncoles@gmail.com
Change-Id: I115ffb1dc601652a979895d7944e011b951a91c1
7e5235894b