Refactor: remove en-IE from Intl.NumberFormat and create a `formatNumber` function

[andreaforni]

In different parts of the app (for example here, here and here) the following line of code is used to format numbers:

new Intl.NumberFormat('en-IE').format(<value>)

We should:

• remove the hardcoded en-IE locale and read the current used by the app so that the numbers can be formatted accordingly
• extract a formatNumber to reduce duplication.