The issue was found during an Item creation inside the Invoice,
Estimates or Recurring Invoice, the same fix that was applied into the
Item creation view, now is needed into ItemModal. The root cause is that
price + tax returns an amount as float making the database fail.
Relates #377
* Possibility to set a fixed amount on tax types settings
* Pint and manage flat taxes on items
* Fix display errors and handle global taxes
* Tests
* Pint with PHP 8.2 cause with PHP 8.3 version it cause workflow error
* Merging percent and fixed amount into one column
* Now display the currency on SelectTaxPopup on fixed taxes
