Migrate attachments to CSS modules

[OEvgeny]

Fixes #

Changelog Entry

(no changelog entry for the refactor)

Description

This migrates the recently done attachments work over to CSS modules because now we can.

Design

Refactored the icon component into a HOC as well:

• reusable icons can be added into centralized CSS module
• configurable via CSS only
• can later be exposed to be used e.g. in Fluent theme package
• uses valibot to validate passed props

Specific Changes

• migrated related components to CSS modules
• removed previous CSS-in-JS modules
• cleaned-up the styleSets
• refactored ComponentIcon
• added missing theme styles
• fixed component build missing plugins from the base config

-

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[compulim]

Nitpicking.