tcfilter: add package for persistent tc ingress filters

tcfilter: add package for persistent tc ingress filters

UCI front-end that installs raw "tc filter ... ingress" expressions on
network devices at boot and re-applies them on ifup, removing them on
stop. The match/action part is entered verbatim as tc syntax; the
package manages the device, the preference number, enable/disable and
persistence. A procd reload trigger re-applies on config changes.

Intended for driving hardware tc-flower offload (e.g. the Realtek DSA
PIE offload) where no higher-level configuration layer exists.

Co-authored-by: OpenWrt AI review account <redacted>
Assisted-by: Claude Code (Anthropic Claude Sonnet 5)
Signed-off-by: Mark Abe <redacted>