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 convert unique_ptrs to shared_ptrs.

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.

Also fixes various style warnings.

Working in Android and ios so far.

Is this worth pursuing further?

[github-actions]

Bloaty Results (iOS) 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  -0.7% -91.0Ki  -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%  +115Ki  +0.0%     +40    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                                            +0.0055         +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