Add androidx.benchmark.iterations argument for controlling measurement iters

Test: ./gradlew benchmark:benchmark-common:cC -P android.testInstrumentationRunnerArguments.androidx.benchmark.iterations=100 -P android.testInstrumentationRunnerArguments.class=androidx.benchmark.BenchmarkStateTest

Fixes: 194137879

Note: this doesn't modify warmup, which is still an arbitrary number
of iterations. The initial intent is to support profiling use cases
(which should use androidx.benchmark.profiling.*), or experimenting
locally when providing feedback on automatic iteration determination.

Change-Id: I1682ccff011f430da564cedf9113fb628b8d87b4

• benchmark/benchmark-common/src/androidTest/java/androidx/benchmark/ArgumentInjectingApplication.kt[diff]
• benchmark/benchmark-common/src/androidTest/java/androidx/benchmark/BenchmarkStateTest.kt[diff]
• benchmark/benchmark-common/src/main/java/androidx/benchmark/Arguments.kt[diff]
• benchmark/benchmark-common/src/main/java/androidx/benchmark/BenchmarkState.kt[diff]
• benchmark/benchmark-junit4/src/androidTest/java/androidx/benchmark/junit4/ArgumentInjectingApplication.kt[diff]