[Subscription Billing]Calculating initial dates correctly

[miljance]

Summary

This pull request primarily simplifies and clarifies the handling of subscription line term calculations and improves the consistency of tooltips across multiple pages. The most significant change is a refactor of the logic for calculating the "Term Until" and "Cancellation Possible Until" dates, removing redundant methods and ensuring that the calculations align more closely with business rules. Additionally, the tooltips for the "Extension Term" field have been standardized across various pages for clarity.

Key changes include:

Subscription line calculation logic refactor

• Removed the CalculateInitialCancellationPossibleUntilDate method from SubscriptionLine and updated the logic in CalculateInitialTermUntilDate to handle both "Term Until" and "Cancellation Possible Until" calculations, streamlining the process and reducing redundancy.
• Updated all relevant codeunits (Sales Documents, Create Subscription Line, Post Sub. Contract Renewal) and the Subscription Header table to remove calls to the now-deleted CalculateInitialCancellationPossibleUntilDate and ensure correct sequencing of term calculations.

UI/UX and documentation consistency

• Standardized the tooltip for the "Extension Term" field across all related pages, removing the previously included conditional explanation and making the description more concise and user-friendly.

Data consistency improvements

• Ensured that the Renewal Term field is now copied from ServiceCommitment to Sub. Contr. Analysis Entry for improved data consistency in contract analysis.

Technical code review from @samra-singhammer or @sit-zm required prior to approval by Microsoft.

Work Item(s)

Fixes #6132