Improve styling of design pins

What does this MR do?

Updates design pins with the following changes (from #219951 (closed)):

• Increase the design pin size to 32 x 32 pixels.
• Increase the border thickness to 2 pixels.
• Pin text: 16px, Bold, White.
• Add a box-shadow to all pins (see below).
• Change the pin background color to #9475DB Purple-400 from Pajamas.
• On hover, the pin will increase in size (see below).
• Disabled pins will still be gray, but will retain all other new stylings.

Pins will have a hover transition for the size increase:

 transform: scale(1.2);
 will-change: transform;
 transition: transform 350ms cubic-bezier(0, 1, 1, 1);

Box-shadow:

box-shadow: 0px 2px 4px rgba(0, 0, 0, 0.32);

Screenshots

New pins on a design

New pin on the comment sidebar

Hover state

pin_hover

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team