Merge changes from topic "cherrypicker-L22800030000756195:N75200030012855151" into main

* changes:
  [nearby] Add nearby_enable_ble_in_init flag
  Revert "[nearby] Add disable logic"
  [nearby] Add disable logic
  [nearby] Log changes
  [nearby] Sync discoveryTimestamp field name
  [nearby] Enable BLE when init
  [nearby] Add logs to broadcaster
  [nearby] Add discoveryTimestamp field
  [nearby] Fix flakeness in the unit test
  [nearby][clean up] Remove useless legacy code
  [nearby] Fix the user-debug only test
  [nearby] Catches NPE in ChreDiscoveryProvider
  [nearby] Update README to add build env script