FINERACT-2455: Add IRR based calculation for working capital schedule model, fix amortization rounding drift, add multiple payment rate change support

[Cocoa-Puffs]

Description

Describe the changes made and why they were made. (Ignore if these details are present on the associated Apache Fineract JIRA ticket.)

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[AshharAhmadKhan]

@Cocoa-Puffs please check the failing logs and rebase to latest.