fix(#3869): Updated Dropdown borders to be the same as Input

[ArakTaiRoth]

dropdown-border-error, dropdown-border-hover, and dropdown-border-error-hover have all been changed to use input.borderWidth.hover to make it the same as the Input component.

[twjeffery]

@ArakTaiRoth I checked these against the Figma input styles. The hover change is right, but the error changes go the wrong way.

Figma has the input borders at 1px default, 1.5px hover, 2px focus, 2px error.

The dropdown was wrong at 2px on hover, so 1.5px is the correct fix. But error and error hover were already right at 2px, and this moves them off spec. Let's keep the hover change and leave error and error hover as they were.

The issue has it backwards on that row. It uses the text input as the reference, but the text input's error border is the one that's off. It should be 2px, not 1.5px.

Two other things this turned up:

1. Text input and text area both have their error border at 1.5px, so they need the opposite fix from this one.
2. Dropdown multiselect has the same 2px hover as the dropdown, so it needs the same change this PR is making.

[ArakTaiRoth]

@ArakTaiRoth I checked these against the Figma input styles. The hover change is right, but the error changes go the wrong way.

Figma has the input borders at 1px default, 1.5px hover, 2px focus, 2px error.

The dropdown was wrong at 2px on hover, so 1.5px is the correct fix. But error and error hover were already right at 2px, and this moves them off spec. Let's keep the hover change and leave error and error hover as they were.

The issue has it backwards on that row. It uses the text input as the reference, but the text input's error border is the one that's off. It should be 2px, not 1.5px.

Two other things this turned up:

1. Text input and text area both have their error border at 1.5px, so they need the opposite fix from this one.
2. Dropdown multiselect has the same 2px hover as the dropdown, so it needs the same change this PR is making.

@twjeffery I believe I fixed all the issues you raised