Prepare for Restarting Models With Segment Level UDQs

[bska]

In particular

• Explicitly include some headers that will not be available through transitive inclusion
• Remove some unneeded objects/helper functions
• Move helper functions into anonymous namespaces where appropriate
• Re-sort #include statements

[bska]

jenkins build this please

[bska]

jenkins build this please

[atgeirr]

jenkins build this please

[bska]

PR approved and build check is green. I'll merge into master.