Extract methods related to String

Extract methods related to string operations out of
SdkSandboxManagerService class

Bug: 308607306
Test: atest SdkSandboxManagerServiceUnitTests
Change-Id: Ie5afd85987d5a9ab8d77433bdc2984e76cc05af9
(cherry picked from commit c8c451e780cee97da59f254b47d772bb76323485)
Merged-In: Ie5afd85987d5a9ab8d77433bdc2984e76cc05af9
5 files changed