Rate limit calls to AM.getMemoryInfo().

Apps do not need to call getMemoryInfo any more than 100 times per
second. Rate limit this API - if apps want to consume information about
their own memory usage, they can use the getMyMemoryState API instead.

Flag: android.app.rate_limit_get_memory_info
Bug: 364312431
Test: atest ActivityManagerTest
Test: manually check logs for cache hits/misses
Change-Id: If2494509d76e269b0ad75d8d73bc6848adab490b