Prepare to move VCN: Define utility lib for IPsec module

This is a preparation CL before moving VCN code from frameworks/base
to p/m/Connectivity/

After VCN is move out of frameworks/base/, the IPsec module will
no longer include PersistableBundleUtils via framework-ike-shared-srcs
but will do that via vcn-utils-framework-ipsec

Bug: 379938062
Flag: EXEMPT; pure refactoring
Test: CtsIkeTestCases, FrameworksIkeTestCases
Change-Id: I2d405be630a05f5019e7711946fa46b4cf2a6ef8