Make use of OZ initializer modifier

[Auryn Macmillan]

By extending OwnableUpgradeable we also extend open zeppelin Initializable contract, which provides the initializer modifier that we can use in setUp functions instead of having additional initialized var in FactoryFriendly contract.

We should update this in Zodiac, along with all of the modules.

• Zodiac
• Reality module
• Bridge module
• Exit module
  • Circulating supply
• Delay modifier
• Scope guard

[Cesar Brazon]

zodiac: #18
reality: gnosisguild/zodiac-module-reality#51
bridge: gnosisguild/zodiac-module-bridge#17
delay: gnosisguild/zodiac-modifier-delay#18
exit: gnosisguild/zodiac-module-exit#31
scope guard: gnosisguild/zodiac-guard-scope#12

[Auryn Macmillan]

Thanks @cbrzn!