Clean up container iterations

- iterate over const where possible
- use a plain ranged for when accessing only the value
- use key iterators when we only iterate over keys
- iterate over keyValueRange when the body accesses both key and value

Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV794
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV795
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV796
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV797
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV798
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV799
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV801
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV802
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV803
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV804
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV805
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV806
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV807
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV808
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV809
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV810
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV811
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV812
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV813
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV814
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV815
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV816
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV817
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV818
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV819
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV820
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV821
Axivion-Id: qt_Add-ons_qtcharts_dev_linux:SV822
Task-number: QTBUG-146050
Pick-to: 6.12
Change-Id: I000a15768dde7f7641524417c6e1c0b8d187ce11
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>