Allow admin to update donor name properly

[ravinderk]

Issue Overview

In above image, we can see that admin can only update donor full name instead of first name and last name separately. which can cause of typos in some places where we are getting the first name only.
For ref: #1132 , #1585, #1481

[ravinderk]

@mehul0810 handle backend and give_profile_editor form case here as we discussed, We will handle frontend case in #1132

[ravinderk]

@mehul0810 As we discuss over the call, donor name is not syncing with user name when update user profile.

[ravinderk]

@mehul0810 As we discussed over this issue site occurring with the donor (without user). Please fix it.