Simplify generic multiple activity handler

[ipcyborg]

Summary

SUMMARY: Infrastructure "Simplify generic multiple activity handler"

Purpose of change

Function generic_multi_activity_handler is quite big and hard to understand.
It is required to simplify it but keep the structure intact as much as possible.
This PR is created as a result of closing PR #33864.

Describe the solution

Simplify generic multiple activity by splitting to chunks and creating specific sub-functions:

• generic_multi_activity_locations: determine all locations for this generic activity
• generic_multi_activity_check_requirement: check if this activity can not be done immediately because it has some requirements
• generic_multi_activity_do: do activity at this location

The main handler and sub-functions should be easier to maintain now.

Some other minor changes:

• Const reference in function parameters and loops.
• Less use of auto when appropriate.

Describe alternatives you've considered

Use stages as described in PR #33864 (this approach was rejected after a discussion).

Additional context

None

[ghost]

Ill test this in a bit, the code changes look good, the structural changes I'll have to test.

[ghost]

Yeah it works fine.