scylla-gdb.py: Add scylla repairs command
scylla-gdb.py: Add scylla repairs command

This command lists all the active repair_meta objects for both repair
master and repair follower.

For example:

(gdb) scylla repairs

 (repair_meta*) for masters: addr = 0x600005abf830, table = myks2.standard1, ip = 127.0.0.1, states = ['127.0.0.1->repair_state::get_sync_boundary_started', '127.0.0.3->repair_state::get_sync_boundary_finished'], repair_meta = {
   db = @0x7fffe538c9f0,
   _messaging = @0x7fffe538ca90,
   _cf = @0x6000066f0000,

 ....

 (repair_meta*) for masters: addr = 0x60000521f830, table = myks2.standard1, ip = 127.0.0.1, states = ['127.0.0.1->repair_state::get_sync_boundary_started', '127.0.0.2->repair_state::get_sync_boundary_started'], repair_meta = {
   _db = @0x7fffe538c9f0,
   _messaging = @0x7fffe538ca90,
  _cf = @0x6000066f0000,

 ....

(repair_meta*) for follower: addr = 0x60000432a808, table = myks2.standard1, ip = 127.0.0.1, states = ['127.0.0.1->repair_state::get_sync_boundary_started', '127.0.0.2->repair_state::unknown'], repair_meta = {
  db = @0x7fffe538c9f0,
  messaging = @0x7fffe538ca90,
  _cf = @0x6000066f0000,

Fixes #7103

avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla