[data grid] Improve localization dx for custom filters

[MBilalShafi]

IMHO this is a bad practice:

const label =
  op?.headerLabel ??
  apiRef.current.getLocaleText(
    `headerFilterOperator${capitalize(op.value)}` as 'headerFilterOperatorContains',
  );

It crashes even though the headerLabel is supposed to be optional.
Not sure how we could improve it (wrap in a try to avoid crashing and render an empty label? check if the translation key exists before calling getLocaleText? Create a getOptionalLocaleText method?), but right now it's a bad DX.

To be clear, this code have been here for ages, it's not a new problem at all, it was already here when I was working on the grid.

Originally posted by @flaviendelangle in #13217 (comment)

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