[android] - rounded zoom when zooming with zoom button controller

[tobrun]

This PR enables the zoom button controller to zoom to rounded values.
eg. map with zoom 1.435 will zoom in to 2 and 3 instead of current 2.435 and 3.435.

This PR also cleans up some duplicate code in MapGestureDetector related to zoom button controller.

cc @LornTao @1ec5
Review @zugaldia

[1ec5]

Checkstyle is failing:

[ant:checkstyle] [ERROR] /bitrise/src/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/Transform.java:177:68: WhitespaceAround: '?' is not preceded with whitespace. [WhitespaceAround]
:MapboxGLAndroidSDK:checkstyle FAILED

FAILURE: Build failed with an exception.

Update: fixed in b8e55c6.

[1ec5]

A similar fix is going into the iOS and macOS SDKs in #8027.

[zugaldia]

Per #8027 (comment) this proposed change will be brought to 5.0 for consistency with iOS.

[zugaldia]

cc: @Guardiola31337 for review.

[tobrun]

On board for adding this but preferably woud hold off merging this PR atm, GLSurfaceView in #8031 will require some rewriting and that would mean double work as this PR could use some finetuning.

[Guardiola31337]

Looks great 👍
BTW, we should discuss code styles, etc. (I'm not a big fan of the ternary operator 😅)

[1ec5]

Since this PR is scheduled for Android SDK v5.0.0, it needs to be rebased and retargeted at the release-ios-v3.5.0-android-v5.0.0 branch.

[tobrun]

Continued in #8299.