refactor(button): use the new tokens (#29561)

Issue number: Internal

---------

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## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- On ionic.button.scss all dependencies to button.scss were removed, to
avoid the old native theme values being mixed on the new ionic theme
button.
- ionic.button.vars.scss partial was removed
- All values were changed to use tokens.
- Updated snapshots that bring slight differences due to now we are
totally using the ionic theme tokens.
- Tests with colors where the ionic button was being added also now have
differences, as the current ion-colors aren't affecting the ionic theme
button. This is expected, as the ionic theme should only work with the
colors from the new Design System, which is something being tacked on
this [PR](#29557). in
the future, we should remove the ionic button from these color ctests
and create new ones that add the new set of colors to the ionic button.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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below.
  2. Update the BREAKING.md file with the breaking change.
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Author: BenOsodrac

core/api.txt

@@ -398,73 +398,50 @@ ion-button,prop,theme,"ios" | "md" | "ionic",undefined,false,false
 ion-button,prop,type,"button" | "reset" | "submit",'button',false,false
 ion-button,event,ionBlur,void,true
 ion-button,event,ionFocus,void,true
-ion-button,css-prop,--background,ionic
 ion-button,css-prop,--background,ios
 ion-button,css-prop,--background,md
-ion-button,css-prop,--background-activated,ionic
 ion-button,css-prop,--background-activated,ios
 ion-button,css-prop,--background-activated,md
-ion-button,css-prop,--background-activated-opacity,ionic
 ion-button,css-prop,--background-activated-opacity,ios
 ion-button,css-prop,--background-activated-opacity,md
-ion-button,css-prop,--background-focused,ionic
 ion-button,css-prop,--background-focused,ios
 ion-button,css-prop,--background-focused,md
-ion-button,css-prop,--background-focused-opacity,ionic
 ion-button,css-prop,--background-focused-opacity,ios
 ion-button,css-prop,--background-focused-opacity,md
-ion-button,css-prop,--background-hover,ionic
 ion-button,css-prop,--background-hover,ios
 ion-button,css-prop,--background-hover,md
-ion-button,css-prop,--background-hover-opacity,ionic
 ion-button,css-prop,--background-hover-opacity,ios
 ion-button,css-prop,--background-hover-opacity,md
-ion-button,css-prop,--border-color,ionic
 ion-button,css-prop,--border-color,ios
 ion-button,css-prop,--border-color,md
-ion-button,css-prop,--border-radius,ionic
 ion-button,css-prop,--border-radius,ios
 ion-button,css-prop,--border-radius,md
-ion-button,css-prop,--border-style,ionic
 ion-button,css-prop,--border-style,ios
 ion-button,css-prop,--border-style,md
-ion-button,css-prop,--border-width,ionic
 ion-button,css-prop,--border-width,ios
 ion-button,css-prop,--border-width,md
-ion-button,css-prop,--box-shadow,ionic
 ion-button,css-prop,--box-shadow,ios
 ion-button,css-prop,--box-shadow,md
-ion-button,css-prop,--color,ionic
 ion-button,css-prop,--color,ios
 ion-button,css-prop,--color,md
-ion-button,css-prop,--color-activated,ionic
 ion-button,css-prop,--color-activated,ios
 ion-button,css-prop,--color-activated,md
-ion-button,css-prop,--color-focused,ionic
 ion-button,css-prop,--color-focused,ios
 ion-button,css-prop,--color-focused,md
-ion-button,css-prop,--color-hover,ionic
 ion-button,css-prop,--color-hover,ios
 ion-button,css-prop,--color-hover,md
-ion-button,css-prop,--opacity,ionic
 ion-button,css-prop,--opacity,ios
 ion-button,css-prop,--opacity,md
-ion-button,css-prop,--padding-bottom,ionic
 ion-button,css-prop,--padding-bottom,ios
 ion-button,css-prop,--padding-bottom,md
-ion-button,css-prop,--padding-end,ionic
 ion-button,css-prop,--padding-end,ios
 ion-button,css-prop,--padding-end,md
-ion-button,css-prop,--padding-start,ionic
 ion-button,css-prop,--padding-start,ios
 ion-button,css-prop,--padding-start,md
-ion-button,css-prop,--padding-top,ionic
 ion-button,css-prop,--padding-top,ios
 ion-button,css-prop,--padding-top,md
-ion-button,css-prop,--ripple-color,ionic
 ion-button,css-prop,--ripple-color,ios
 ion-button,css-prop,--ripple-color,md
-ion-button,css-prop,--transition,ionic
 ion-button,css-prop,--transition,ios
 ion-button,css-prop,--transition,md
 ion-button,part,native