FEA: add new features from pymr's doublespinbox

Features to be added based on pymr's doublespinbox

• Remove zero truncation
• New behaviour: Move cursor to the end of numeric part when entering a number with left-placed zeroes like '0005.001'.
• Fix wrong cursor position handling when entering numbers that receives thousand separators.

These features were proposed on https://gitlab.com/CIERMag/pymr/-/issues/459.

Note that the proposed 'Fix wrong cursor position handling when entering numbers that receives thousand separators.' on pymr doesn't apply to pqwidget since this bug doesn't exist here.