Frontend changes for User Permission export

What does this MR do?

This MR adds a icon for User Permission Export in the Users section of the Admin dashboard.

Mentions #273496 (closed)

Screenshots (strongly suggested)

Before	After

On email icon hover

On export icon hover

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When export_user_permissions feature is not available:

Feature Flag

export_user_permissions_feature_flag, defaulted to false.

Please note, no Changelog has been included in this MR accordingly.

Conformity

• [-] Changelog entry
• [-] Documentation (if required) (will be included in a seperate MR)
• 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