Change Python in Soong to support device side build.

Add python_test to generate executables for both host and device side.
And change python_library_host to python_library.

installation for python device test will be under
target/product/generic_arm[64]/data/nativetest[64].

Bug: b/69114465
Test: m clean && m -j
Device Test:
adb root; adb push nan_devicetest /data;
adb shell; ./nan_devicetest
print(sys.path)
['/data/nan_devicetest/runfiles', '/data/nan_devicetest', '/data/nan_devicetest/internal', '/data/nan_devicetest/internal/stdlib']

Change-Id: If8317070a3aa1b6dab2e84b8df2d037f495d7247