Adds differentiation between acting and interim positions

Why is this change being made?

There are two types of temporary leadership roles:

• ones where the person is truly occupying the role temporarily
• ones where the person is working on a promotion doc to fill the role permanently

This MR defines "acting" and "interim" to clarify the difference between these.

This is an alternate proposal to !43780 (closed)

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what