Replace LocationProvider with ProviderProperties

LocationProvider cannot represent unknown properties, which is currently
causing problems with getProvider() which may return null even when a
particular provider exists. Instead provide isProvider() to query
whether a provider exists, and getProviderProperties() to query a
provider's properties.

Bug: 176232308
Test: atest CtsLocationNoneTestCases
Change-Id: Ic42cc953624be116616b0b997e18356247fdf288