Form field Floating labels gaps not customizable and not taking into account the label actual size

#### Feature Description
So here is the thing. Since no dense mode and since we have a custom looking material inputs, I had to make my own customization on the scss theme of the form field. The problem appeared when I changed the font size and the font itself of the floating label. Suddenly I saw that the borders are overlapping the text.
```
const floatingLabelScale = 0.75;
const outlineGapPadding = 5;
```
these values are based on some assumption that the label size will never be customized.
Now, in order to override this behavior I had to create my own directive that changes the values
and recalculate the gaps.
So I would like to request a change of this logic to calculate gaps dynamically, or to expose these 2 numbers as inputs or something that can be changed from outside. I'm ok with an injection token as well.

#### Use Case

In order to allow more customization features and be able to change the font-size of the floating label.

Beginne damit, die Angular Material form-field-Implementierung zu lokalisieren, die die Skalierung schwebender Labels und die Werte für Outline-Lücken definiert, und reproduziere dann das Problem mit einer benutzerdefinierten Label-Schriftart und -größe. Bestimme, ob die Lücken dynamisch berechnet oder zur Konfiguration bereitgestellt werden sollten; als erledigt gilt, wenn angepasste Labels die Rahmen nicht mehr überlappen.

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