[FR]: Separate gtest and gmock cmake target

### Does the feature exist in the most recent commit?

No.

### Why do we need this feature?

Hi, I'm using gtest by CMake under OpenSUSE. However, I noticed that gtest package doesn't contain cmake config files. All gtest and gmock cmake config files are contained in gmock package. The root problem is gtest and gmock cmake target is contained in one cmake file. Many Linux distributions split package as modular as possible. I hope cmake config files can be separated as pkgconf files.

### Describe the proposal.

Make gtest and gmock cmake targets exist in different files.

### Is the feature specific to an operating system, compiler, or build system version?

No.

No specific files or tests are named. Start by locating the CMake file that currently defines both gtest and gmock targets and inspect how the package config files are generated; done means gtest and gmock targets and their CMake config files can be packaged separately.

Written by the indexing model from the issue text.