Some fixes to power manager lib code

- Run clang-format on all recently added files;
- Move all new classes to android::power namespace and remove Power
prefix from all classes and enums;
- Add virtual function specifier to overrides of virtual members;
- Add missing virtual destructors;
- Remove namespaces and aliases from public api of header files;
- Delete constructor and destructor of PowerHalLoader;
- Add helper functions to convert hal results in wrapper
implementations;
- Merge test targets to single libpowermanager_test target;

Bug: 150878220
Test: atest libpowermanager_test
Change-Id: Ie2b5ad69f3b05d5f6b576671bc98e0f83b274152