[Revolving] merge cashflow

[yellowbean]

Issue

If original pool cashflow date range : 2024-01-01 -> 2024-12-01 but the new bought cashflow from revolving pool is 2024-06-01 -> 2025-03-01

In current merging logic, the cashflow from 2024-12-01 -> 2025-03-01 will be dropped.

Solution

• Merge cashflow A with new bought cashflow B

• if time horizon of cashflow A is shorter than cashflow B ?

• The engine should expand the dates of cashflow A with deal Pool Freq

[yellowbean]

fix 7ae5883