CMake: Set CMAKE_POLICY_VERSION_MINIMUM with older Android NDKs

When using CMake 3.31+ with Android NDKs older than r28, CMake shows
the following deprecation warning:

CMake Deprecation Warning at
ndk/27.2.12479018/build/cmake/android.toolchain.cmake:35
  (cmake_minimum_required):
  Compatibility with CMake < 3.10 will be removed from a future
  version of CMake.

This warning appears multiple times, when configuring Qt, user
projects, try_compile calls, etc.

That's because the Android NDK cmake toolchain file sets
cmake_minimum_required(VERSION 3.6) unconditionally, which is less
than 3.10.

To avoid the warnings, we can set the CMAKE_POLICY_VERSION_MINIMUM
variable or environment variable to 3.10.
The variable can only be set in CMake 4.0+ though, so it won't help
with CMake 3.31.

The assignment has to be done in multiple places:
- When detecting Android in QtAutoDetectHelpers.cmake
- When generating the Qt toolchain file in QtToolchainHelpers.cmake
- When doing try_compile calls in QtFeature.cmake
- When doing test calls in QtRunCMakeTestWrappers.cmake

To be on the safer side, the following opt-outs are provided:
- QT_NO_SET_ANDROID_CMAKE_POLICY_VERSION_MINIMUM
    If set to true, the automatic setting of
    CMAKE_POLICY_VERSION_MINIMUM is disabled.
- QT_ANDROID_CMAKE_POLICY_VERSION_MINIMUM
    A version to use instead of 3.10.
- QT_NO_SET_RUN_CMAKE_TESTS_CMAKE_POLICY_VERSION_MINIMUM
    Disables the assignment for RunCMake tests.

These are considered at various points in the code, rather than just
once when configuring Qt.

When using NDK r28 or newer, the toolchain file sets 3.10 itself, so
no warning appears.

Pick-to: 6.8 6.10
Change-Id: I47c6013f9cafed8836c32d2b726e75838c9d8779
Reviewed-by: Joerg Bornemann <[email protected]>
Reviewed-by: Assam Boudjelthia <[email protected]>

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