* Set default style to link-button mixin
It was identified that we currently have 3 different behaviors for links used in the application. In issue woocommerce/woocommerce-blocks#1778, it was discussed a set of good practices that we should follow in order to obtain consistency between links.
Currently, the link-button mixin is already used by the 'Clear all' button in the Active Filters block, so the idea was to increment it with a common pattern (font size small, font-weight normal, underlined by default and not underlined when on hover) that can be reused by other components (for example FilterResetButton).
* Change link-button mixin to make it attend the expected default style for links
* Replace text-button with link-button mixin in FilterResetButton component
* Add new mixin for links in filter blocks
* Revert change to link-button mixin to prevent it to affect link buttons on Checkout page
* Add filter-link-button mixin that can be used in filter blocks
* Remove link-button styles that were moved to filter-link-button mixin
By default, link-button mixin styles should have only styles from the text-button mixin and also be underlined.
The styles for link button in filter blocks should reside in filter-link-button mixin.