fix(buttons): Update button states to match specs

What does this MR do?

Button	State	Before	After
Default	Resting
Default	Hover
Default	Focus
Default	Active
Default	Selected
Dashed	Resting
Dashed	Hover
Dashed	Focus
Dashed	Active
Disabled	Resting
Loading	Resting
Label	Resting
Primary Info	Resting
Primary Info	Hover
Primary Info	Focus
Primary Info	Active
Secondary Info	Resting
Secondary Info	Hover
Secondary Info	Focus
Secondary Info	Active
Primary Success	Resting
Primary Success	Hover
Primary Success	Focus
Primary Success	Active
Secondary Success	Resting
Secondary Success	Hover
Secondary Success	Focus
Secondary Success	Active
Primary Warning	Resting
Primary Warning	Hover
Primary Warning	Focus
Primary Warning	Active
Secondary Warning	Resting
Secondary Warning	Hover
Secondary Warning	Focus
Secondary Warning	Active
Primary Danger	Resting
Primary Danger	Hover
Primary Danger	Focus
Primary Danger	Active
Secondary Danger	Resting
Secondary Danger	Hover
Secondary Danger	Focus
Secondary Danger	Active
Button link	Resting
Button link	Hover
Button link	Focus
Button link	Active

Does this MR meet the acceptance criteria?

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.

Closes #838 (closed)