feat(tab-button): update styles to iOS 17 specs (#28754)

Issue number: Internal

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->
Tab Button icons on iOS are all 30px font size with or without a label.

![Screenshot 2023-12-21 at 2 12
56 PM](https://github.com/ionic-team/ionic-framework/assets/14926794/5321e0cd-6315-4557-8ec3-4dae8a3728cb)


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

- Tab button icons are still 30px font size when there is no label
- Tab button icons are 24px font size when there is a label

![Screenshot 2023-12-21 at 2 12
29 PM](https://github.com/ionic-team/ionic-framework/assets/14926794/e65060c8-e394-43d2-a713-2e0a2a78550a)




## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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screenshots of how the component looks before and after the change. -->

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Co-authored-by: ionitron <hi@ionicframework.com>

core/src/components/tab-button/tab-button.ios.scss

@@ -140,6 +140,12 @@
   @include position(10px, null, null, null);
 }
 
+// Icon
 :host(.tab-layout-label-hide) ::slotted(ion-icon) {
   @include margin(0);
 }
+
+:host(.tab-layout-label-hide) ::slotted(ion-icon),
+:host(.tab-has-icon-only) ::slotted(ion-icon) {
+  font-size: $tab-button-ios-icon-only-size;
+}

core/src/components/tab-button/tab-button.ios.vars.scss

@@ -24,5 +24,8 @@ $tab-button-ios-text-color:           $tabbar-ios-color !default;
 /// @prop - Font size of the tab button text
 $tab-button-ios-font-size:            10px !default;
 
-/// @prop - Size of the tab button icon
-$tab-button-ios-icon-size:            30px !default;
+/// @prop - Size of the tab button icon when there is a label
+$tab-button-ios-icon-size:            24px !default;
+
+/// @prop - Size of the tab button icon when there is not a label
+$tab-button-ios-icon-only-size:       30px !default;