feat: add a multiplier to replace the potentially confusing value_factor

[mflagler]

Scaling values using the value_factor is too difficult. This should simply be a multiplier, not a factor/exponent of 10 that you want to scale values by. For converting MB to GB or GB to MB it makes it much easier, and for anything that is scaled by 10s then you just multiply by the factor of 10, 100, or 0.1, or 0.01 and it's plain and simple. There should be a pre-scale offset and a post-scale offset for anyone wanting to convert temps between C and F. Then you could pretty much convert between any units anyone should ever need.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. If this is still an active issue, please let us know!

[stale]

Still an active issue, got it! Removing stale label.

[ildar170975]

In the Docs:

IMHO the value_factor should be ANY number [-xxx.xxx, +xxx.xxx].
Values like "0.9, 0.5, 0.04" should scale the state down.
Values like "1.2, 25, 400.56" should scale the state up.
Negative values should make the state negative.

Also, should be specified per-entity - #607

[jlsjonas]

We should add a simpler multiplier (or similar) property and deprecate value_factor to be removed at a later date (also see #608)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. If this is still an active issue, please let us know!

[RcRaCk2k]

Yeah, i also need that.

Having costs per kWh and a cost average for the last hour. So the line of costs per kWh is so small that you can not see any changes in the cent-values, so i have to multiply that bei 5 times, so i can see the price changes in the chart.

[Danie10]

I was also looking for this as I have a forecasted solar radiation in W/m2, and it needed to be multiplied by a factor of 15.57 to equate to the same power as the area of my solar panels. Was looking to have a 'value_factor: 15.57' for that entity.