Eliminate copies in deferred cleanup

[TimSylvester]

Pulls in an implementation of move_only_function.

This simplifies deferred deletions, since there's no temporary copy to potentially outlast the schedule call, and eliminates the need to transfer ownership from each unique_ptr to a shared_ptr so that it can be copied.

Unfortunately, the change of function types for the scheduler spreads to the map callbacks due to usage like:

pathChangeCallback = Scheduler::GetCurrent()->bindOnce(...

This is further complicated by the fact that of the callbacks are explicitly copied:

void FileSourceRequest::setResponse(const Response& response) {
    // Copy, because calling the callback will sometimes self
    // destroy this object. We cannot move because this method
    // can be called more than once.

So some but not all callbacks are changed to the new function type, and typedefs are added to clarify.

This will make it possible to eliminate the extra copy steps in deferred tile destruction.

[github-actions]

Bloaty Results (iOS) 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  -0.6% -74.8Ki  -0.5% -64.0Ki    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results-ios/pr-3035-compared-to-main.txt

[github-actions]

Bloaty Results 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.1%  +114Ki  -0.0%    -224    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-3035-compared-to-main.txt

Compared to d387090 (legacy)

    FILE SIZE        VM SIZE    
 --------------  -------------- 
   +31% +36.2Mi  +438% +26.2Mi    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-3035-compared-to-legacy.txt

[github-actions]

Benchmark Results ⚡

Benchmark                                                     Time             CPU      Time Old      Time New       CPU Old       CPU New
------------------------------------------------------------------------------------------------------------------------------------------
OVERALL_GEOMEAN                                            -0.0053         -0.0052             0             0             0             0

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/benchmark-results/pr-3035-compared-to-main.txt

[louwers]

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