Adding service account

[ihoroleksiienko]

Main Changes

This pull request adds temporary solution for testing that will be removed in the future. It adds a service testing account to BalanceTracker in the getDailyBalances() function with conditions:

• if the day index is less or equal 19703 (12 Dec 2023 BRT), the function provides 10 000 BRLC as the balance of the account;
• if the day index is higher than 19703, the function provides the actual balance of the account.

These changes lead to increased yield for the service account in the YieldStreamer contract.

Test coverage

File	% Stmts	% Branch	% Funcs	% Lines
contracts/	94.37	66.67	87.88	94.37
BRLCToken.sol	100	66.67	100	100
BRLCTokenBridgeable.sol	86.67	66.67	71.43	86.67
InfinitePointsToken.sol	100	66.67	100	100
LightningBitcoin.sol	100	66.67	100	100
USJimToken.sol	86.67	66.67	71.43	86.67
contracts/base/	99.35	100	98.11	99.49
ERC20Base.sol	100	100	100	100
ERC20Bridgeable.sol	100	100	100	100
ERC20Freezable.sol	95.83	100	88.89	96.88
ERC20Hookable.sol	100	100	100	100
ERC20Mintable.sol	100	100	100	100
ERC20Restrictable.sol	100	100	100	100
contracts/base/common/	100	100	100	100
BlacklistableUpgradeable.sol	100	100	100	100
PausableExtUpgradeable.sol	100	100	100	100
RescuableUpgradeable.sol	100	100	100	100
contracts/periphery/	100	97.18	100	100
BalanceTracker.sol	100	94.74	100	100
YieldStreamer.sol	100	98.08	100	100
contracts/base/interfaces/	100	100	100	100
contracts/base/interfaces/periphery/	100	100	100	100
contracts/mocks/	93.18	83.33	100	95.83
contracts/mocks/base/	100	100	100	100
contracts/mocks/base/common/	100	100	100	100
--------------------------------------	----------	----------	----------	----------
All files	91.35	87.55	87.35	91.74
--------------------------------------	----------	----------	----------	----------