DO NOT MERGE: Context#startInstrumentation could be started from SHELL only now.

Or, if an instrumentation starts another instrumentation and so on,
and the original instrumentation is started from SHELL, allow all
Context#startInstrumentation calls in this chain.

Otherwise, it'll throw a SecurityException.

Bug: 237766679
Test: atest CtsAppTestCases:InstrumentationTest
Merged-In: Ia08f225c21a3933067d066a578ea4af9c23e7d4c
Merged-In: I1b76f61c5fd6c9f7e738978592260945a606f40c
Merged-In: I3ea7aa27bd776fec546908a37f667f680da9c892
Change-Id: I7ca7345b064e8e74f7037b8fa3ed45bb6423e406