[low-power] implement enhanced-ack based probing (#5780)

This commit implements Enhanced-ACK Probing (on simulation platform).

- Add a new public API otLinkMetricsConfigEnhAckProbing which sends
  Link Metrics Management Request to configure the probing. This is
  called on Probing Initiator side.

- Add a new radio platform API otPlatRadioConfigureEnhAckProbing. This
  API should be called on Probing Subject side when handling the
  requests from Initiators. This API notifies the radio to start/stop
  aggregating link metrics info and include the data into Vendor IE in
  enhanced-ACK for the specific neighbor. As discussed in #5746, the
  code for doing such thing should be put in radio driver.

- Add a util module util/link_metrics, which provides a group of APIs
  to implement Probing Subject side logic for Enh-ACK Probing. Any
  platform could use this module to implement the feature easily in
  radio driver.

- Add new util APIs in util/mac_frame to generate Enh-ACK Probing IE
  (Vendor IE with Thread OUI and SubType = 0) and set value for this
  IE.

- Update the implementation in simulation/radio.c to support Probing
  Subject side logic for Enh-ACK Probing, using APIs in
  util/link_metrics and util/mac_frame.

- Add a test
  v1_2_LowPower_7_1_01_SingleProbeLinkMetricsWithEnhancedAcks.py for
  testing.

Misc:

  - Add check for all the public Link Metrics APIs (Initiator side) to
    ensure that the Subject is a neighbor of the Initiator. If the
    address is not link-local or the neighbor is not found, an error
    UNKNOWN_NEIGHBOR would be returned.

  - Update PrepareEmptyFrame so that when it's called for reference
    device, its frame version would be set to 2015.

tests/scripts/thread-cert/pktverify/layer_fields.py

@@ -275,6 +275,7 @@ _LAYER_FIELDS = {
     'wpan.channel': _auto,
     'wpan.header_ie.id': _list(_auto),
     'wpan.header_ie.csl.period': _auto,
+    'wpan.payload_ie.vendor.oui': _auto,
 
     # MLE
     'mle.cmd': _auto,
@@ -320,13 +321,16 @@ _LAYER_FIELDS = {
     'mle.tlv.addr16': _auto,
     'mle.tlv.channel': _auto,
     'mle.tlv.addr_reg_iid': _list(_auto),
+    'mle.tlv.link_enh_ack_flags': _auto,
     'mle.tlv.link_forward_series': _list(_auto),
+    'mle.tlv.link_requested_type_id_flags': _list(_hex),
     'mle.tlv.link_sub_tlv': _auto,
     'mle.tlv.link_status_sub_tlv': _auto,
     'mle.tlv.query_id': _auto,
     'mle.tlv.metric_type_id_flags.type': _list(_hex),
     'mle.tlv.metric_type_id_flags.metric': _list(_hex),
     'mle.tlv.metric_type_id_flags.l': _list(_hex),
+    'mle.tlv.link_requested_type_id_flags': _bytes,
 
     # IP
     'ip.version': _auto,