Stop overwrite sdk version

[xiaomi7732]

It doesn't make sense to have this enhancer to carry a separate SDK version. That actually created quite a confusion on the support side.

For the backward compatibility, we should also expose a switch to allow keep the sdk version.

For example:

KeepUsingCustomSDKVersion = `true` | `false` and default to `false`.

Break down the tasks:

[ ] Stop overwriting sdk version;
[ ] Add an option to allow the end user choose to keep writing the sdk version;
[ ] Update document about the configuration.