Overhaul core Tracker: add tests for `whitelist` mod

[josecelano]

Parent issue: #1226

Coverage before:

Filename                                                                    Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
packages/tracker-core/src/whitelist/authorization.rs                             18                 0   100.00%           8                 0   100.00%          46                 0   100.00%           0                 0         -
packages/tracker-core/src/whitelist/manager.rs                                   49                 7    85.71%          21                 3    85.71%         113                 7    93.81%           0                 0         -
packages/tracker-core/src/whitelist/mod.rs                                       13                 0   100.00%           4                 0   100.00%          33                 0   100.00%           0                 0         -
packages/tracker-core/src/whitelist/repository/in_memory.rs                      28                 0   100.00%          16                 0   100.00%          85                 0   100.00%           0                 0         -
packages/tracker-core/src/whitelist/repository/persisted.rs                      22                 6    72.73%           4                 0   100.00%          24                 2    91.67%           0                 0         -
packages/tracker-core/src/whitelist/setup.rs                                      1                 0   100.00%           1                 0   100.00%           7                 0   100.00%           0                 0         -
packages/tracker-core/src/whitelist/whitelist_tests.rs                            3                 0   100.00%           2                 0   100.00%          11                 0   100.00%           0                 0         -