fix: amountInput for 18 units

[LuizAsFight]

Closes FRO-121

There were bugs when using AmountInput with 18 units:

• was not working to type after 9 decimal units (0.000000001)
• was not working to set balance with more than 9 decimal units
• value was not showing correctly for more than 9 decimal units
• balance showing incorrectly

This PR:

• completely fixes the usage of AmountInput
• split some tests and also create new ones to cover bugged scenarios
  • applied tests to both 9 and 18 units

[github-actions[bot]]

Coverage report for ./design-system/react

St.:grey_question:	Category	Percentage	Covered / Total
🟢	Statements	94.45%	1922/2035
🟢	Branches	82.65%	381/461
🟢	Functions	85.66%	233/272
🟢	Lines	94.87%	1888/1990

Test suite run success

183 tests passing in 47 suites.

Report generated by 🧪jest coverage report action from 5962b1e09f5bd87b722868cbfd6eba1cd59b8cc9