[xp] refactor signature class

Coverage report for experimental massa-web3

St.^{:grey_question:}	Category	Percentage	Covered / Total
🔴	Statements	46.53% (+0.22% 🔼)	683/1468
🔴	Branches	21.76% (-0.23% 🔻)	84/386
🔴	Functions	38.59% (+0.21% 🔼)	115/298
🔴	Lines	46.33% (+0.22% 🔼)	670/1446

Show files with reduced coverage 🔻

St.^{:grey_question:}

| File | Statements | Branches | Functions | Lines | | :-: | :- | :- | :- | :- | :- | | 🟢 |

`...` / address.ts

92.54% (-2.38% 🔻)

60% (-9.23% 🔻)

| 100% |

92.54% (-2.38% 🔻)

| | 🟡 |

`...` / signature.ts

63.33% (-8.1% 🔻)

20% (-13.33% 🔻)

85.71% (+2.38% 🔼)

63.33% (-8.1% 🔻)

47 tests passing in 7 suites.

Report generated by 🧪jest coverage report action from 63e361dde97a3f90394db06a2a78e94e0424e8a4