[Extensibility][SubscriptionBilling]: Add PostingDate parameter to OnBeforeReleaseCustomerContractDeferral and OnBeforeReleaseVendorContractDeferral integration event for 28.x

[miljance]

What & why

This is a backport of #7981
Added PostingDate as a parameter to the OnBeforeReleaseCustomerContractDeferral and OnBeforeReleaseVendorContractDeferral integration events in ContractDeferralsRelease.Report.al.

Previously, subscribers had no way to access the posting date at the time these events were raised. The PostingDate is now exposed as a read-only parameter, allowing subscribers to act on or conditionally respond to the posting date as part of their event handling logic.

Linked work

Fixes #7980
Fixes AB#635032

How I validated this

• I read the full diff and it contains only changes I intended.
• I built the affected app(s) locally with no new analyzer warnings.
• I ran the change in Business Central and confirmed it behaves as expected.
• I added or updated tests for the new behavior, or explained below why none are needed.

Risk & compatibility

This is a backport, no risks observed.