fix(filter-menu-button, filter-button): improve container contrast

[saiponnada]

Fixes #1985

• This PR contains CSS changes
• This PR does not contain CSS changes

Description

Added default border for filter-button, filter-menu-button and filter-link in enabled state and a strong border on focus.

Notes

The color tokens being considered currently might not be accurate as per design requirements and might need an update.

Screenshots

filter-button, filter-link

Before

After

filter-menu-button

Before

After

Checklist

• I verify the build is in a non-broken state
• I verify all changes are within scope of the linked issue

• I regenerated all CSS files under dist folder
• I tested the UI in all supported browsers
• I did a visual regression check of the components impacted by doing a Percy build and approved the build
• I tested the UI in dark mode and RTL mode
• I added/updated/removed Storybook coverage as appropriate