[XL] Fix the updating IDs behavior

[jgeurten]

Issue:

• Several customers have filed feedback that the constant updating of File and Signer rule IDs update every time they edit their policy.
• This is a default behavior of the PS cmdlets merge command to ensure uniqueness
• Since each custom rule in the Wizard used to create its own policy which were merged together in the final step, policy IDs updated often

Fix:

• The fix involves changing the behavior from storing each rule in a policy on disk to storing in an SiPolicy object and continuously updating it with the new rules
• Additionally, all new rules added to the object are generated with a monotonically increasing ID to ensure uniqueness

Closes #399