fix(Link): Add support to allow only safe urls

Follow-up MR !1432 (closed)

What does this MR do?

This MR ports the SafeLink component to GlLink Component which would mean that GlLink would no longer allow any unsafe urls.

Implementation

• GlLink should be rendered as span tag when href provided is not safe.
• Add support to consider fragment urls as safe (not covered by SafeLink component)

There is a separate MR which would deprecate the SafeLink Component, replacing it with GlLink.

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
• If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• If the MR changes a component's API, integration MR(s) have been opened in the following projects to ensure that the @gitlab/ui package can be upgraded quickly after the changes are released:
  • GitLab: mr_url
  • Customers Portal: mr_url
  • Status Page: mr_url
• Added the ~"component:*" label(s) if applicable.