feat: Add cache_clear method to AdGuardHome class

[BobcatProgrammer]

Proposed Changes

This commit adds a new method cache_clear to the AdGuardHome class in the adguardhome.py file. The cache_clear method allows clearing the cache of the AdGuard Home instance. It sends a POST request to the /control/cache_clear endpoint.

This change was made to provide a convenient way for users to clear the cache of the AdGuard Home instance.

Related Issues

#1095