[1/?] Support android.content for Ravenwood.

Initial pass at foundational classes under android.content, along
with CTS to verify consistency.

Methods that interface to broader parts of OS remain marked as
"throw" for the moment, such as cross-process work and StrictMode.

Bug: 292141694
Test: atest-dev CtsOsTestCasesRavenwood CtsOsTestCases
Test: atest-dev CtsContentTestCasesRavenwood CtsContentTestCases
Change-Id: Ic3deafb1f4058fcc104882a3508728994669f7d2