Remove references to `getFastTextWidth`

[BeksOmega]

Use getTextWidth instead. getFastTextWidth relies on already knowing about the styling that will be applied to the text, which we can't guarantee now that we're styling with CSS.

To work on this, please comment below asking to be assigned.

This change should be made against the rc/v12.0.0 branch.

[BeksOmega]

@ga-fleury is working on this

[AbhinavKRN]

Hey @BeksOmega , i can see no one is assigned on this issue, it would be great if you assign this issue to me?

[BeksOmega]

Heya @AbhinavKRN ga-fleury has a PR up for this at the moment, but if they end up not completing it I'll reassign to you =)

[AbhinavKRN]

@BeksOmega Sure!

[Apocalypse96]

@BeksOmega I would love to solve this issue

[sachan13harshit]

@BeksOmega can you pls assign it to me?

[BeksOmega]

Closed by #8307