[CallingIdentityTokenDetector] New issue - result of clearCallingIdentity()...

[CallingIdentityTokenDetector] New issue - result of clearCallingIdentity() not stored in a variable

If the result of clearCallingIdentity() is not stored in a variable, it
would be impossible to restore the calling identity which could lead to
potential security vulnerabilities with identity.

The detector reports the issue if the immediate parent of
clearCallingIdentity() is not of type ULocalVariable.

Bug: 193779272
Test: atest AndroidFrameworkLintCheckerTest --host
Change-Id: Ic9a384ef33ac7fef6da5145bdd461e7c93d83310