[RESTRICT AUTOMERGE][SettingsProvider] key size limit for mutating settings

Prior to targetSdk 22, apps could add random system settings keys which
opens an opportunity for OOM attacks. This CL adds a key size limit.

BUG: 239415997
Test: manual; will add cts test
Merged-In: Ic9e88c0cc3d7206c64ba5b5c7d15b50d1ffc9adc
Change-Id: Ic9e88c0cc3d7206c64ba5b5c7d15b50d1ffc9adc
(cherry picked from commit 783bcba343c480f6ccedaaff41ba7171a1082e0c)
(cherry picked from commit f60e5a4b7ce47d21a6e707fdad7a865dc0b0f0a3)
Merged-In: Ic9e88c0cc3d7206c64ba5b5c7d15b50d1ffc9adc
2 files changed