Update icon set with lighter stroke weight

Purpose

Replacing existing icons with new lighter weight stroke counterparts.

Screenshots

Before	After

Out of scope

• Angle icons (these will eventually be replaced with the chevrons and it'll make it easier to spot in the UI).
• Pipeline icons.
• 12px status icons.
• Issue type icons.
• Logo icons.

Checklist

For a new icon and/or illustration:

• If this adds an icon ensure that it follows the new icon checklists.
• If this adds an illustration ensure that it follows the new illustration checklists.

Closes #178 (closed)