refactor(mainnet): pallet_proxy config & tests

[al3mart]

Extends proxy config module for the pallet:

• pallet_proxy

Notable configuration items are:

• pallet_proxy

Updated deposits for mainnet runtime:

// One storage item; key size 32, value size 16.
pub const ProxyDepositBase: Balance = deposit(1, 48);
// Additional storage item size of AccountId 32 bytes + ProxyType 1 byte + BlockNum 4 bytes.
pub const ProxyDepositFactor: Balance = deposit(0, 37);
// One storage item; key size 32, value size 16.
pub const AnnouncementDepositBase: Balance = deposit(1, 48);
// Additional storage item 32 bytes AccountId + 32 bytes Hash + 4 bytes BlockNum.
pub const AnnouncementDepositFactor: Balance = deposit(0, 68);

type MaxPending = 32;
type MaxProxies = 32;

[sc-2205]