fix(input): adjust colors, padding, fonts & heights for ionic theme (#29520)

Issue number: internal

---------

## What is the current behavior?
Input styles were slightly different from the ionic theme design. 

## What is the new behavior?
Updates the following:
- The font size for input (14px) and labels (12px)
- The font weight, line-height and color for the label
- The padding for the label & helper message
- Removes the label transform in order to set `font-size` directly
- Updates the Sass variables to be referenced from `tokens` where they
were not

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

## Other information

The underline (undefined) fill looks off from the design but issue
ROU-5151 exists for implementing it so I assume it will be fixed there.

- [Shapes
preview](https://ionic-framework-git-fix-input-placeholder-ionic1.vercel.app/src/components/input/test/shape?ionic:theme=ionic)
- [Fills
preview](https://ionic-framework-git-fix-input-placeholder-ionic1.vercel.app/src/components/input/test/fill?ionic:theme=ionic)

## Image Comparison

| Before | After | UX Design |
| ---| ---| ---|
|
![ionic-before](https://github.com/ionic-team/ionic-framework/assets/6577830/14158641-1118-498a-b970-c277ad505583)
|
![ionic-after](https://github.com/ionic-team/ionic-framework/assets/6577830/fbd1d167-ac3c-4fa7-817d-c5a4ac8b8d3c)
| ![UX
design](https://github.com/ionic-team/ionic-framework/assets/6577830/a3d06503-ce9e-4b15-a1ad-6d11615ec673)
|

> [!NOTE]
> The design is not going to match perfectly because we are not using
the Inter font in our tests.