pbr: update to 1.2.1-r87

pbr: update to 1.2.1-r87

Makefile:
* Remove installation of /usr/share/nftables.d/* files as they are no
  longer needed

Init script:
* bugfixes/more mature netifd extensions support
* refactor of the nft_file function and global variables it uses
* the "main" atomic nft file now includes creation of pbr chains and jumps
  from relevant fw4 chains to pbr chains
* more consistent use of "uplink" wording in the output and variable names
* implement resolver 'wait' call and use it before trying to resolve any
  policy entries
* major overhaul of the split uplink case (IPv4-only wan and IPv6-only
  wan6), should now create/use a single pbr_wan table for both legacy and
  IPv6 routing and the same marking chain
* updates to IDs and text of some error messages (needs luci app update)
* major speed improvements for service stop
* unify the cleanup_* functions into a single cleanup function
* reject creating/additions to nft sets for src_address entries as dnsmasq
  doesn't populate sets with local addresses
* minor bugfixes/code cleanups
* refactor processing of WG servers due to split uplink support (thanks
  @egc112!)
* clearer (hopefully) argument names for process_interface calls
* small improvements to status_service

Signed-off-by: Stan Grishin <redacted>