Optimise icon management

[tobrun]

closes #7343

[tobrun]

been adding tests to potentially cherry pick this PR to release branch, been hitting some compability issues with android OS versions. KitKat and below suffer from a bitmap recycling issue. For now I'm going to turn off recycling for these OS versions.

FYI:

This is memory consumption with Bitmap recycling:

This is consumption without recycling:

[zugaldia]

Great improvement.

This is memory consumption with Bitmap recycling:

What was the scenario in this case (how many icons, size...). Wondering if we could estimate an approximate percentage of memory saved by this change for a typical scenario.

[tobrun]

What was the scenario in this case (how many icons, size...).

Shown graph is after having executed all the tests from IconTest.java (at that time it was 5 or 6 tests). This means we have created 5-6 different Activities with each Activity having it's own map and icons. The lowering of memory = recycling of bitmaps.

Wondering if we could estimate an approximate percentage of memory saved by this change for a typical scenario.

Memory saved is the same as the memory footprint of the bitmap released.

[tobrun]

@zugaldia could you review this? Would love get this in master so we can kick the tires on it.