Cache boot classpath checksums at runtime init. To speed up oat file checksums check. Test: test.py Bug: 191828947 (cherry picked from commit bbdb1ed109532f42949f84194e7717453f2f37f6) Change-Id: I2e469793fccac543517a936dd764530ac1c1d2c7 Merged-In: I2fe97a5626220470ec3edf457a3a24e7d50ce6d7