[FEATURE] Decouple mandates from payment methods for recurring payments

[tinu-hareesswar]

Feature Description

Currently all our recurring payments are wrapped under a mandates layer which is in turn linked to a set of payment methods. We will decouple this and start using the payment methods directly for recurring payments (unscheduled MITs). The mandates would be kept for constrained/scheduled recurring payments.

Possible Implementation

Payments Core changes

• [x] #3753
• [x] #3747
• [x] #3745
• [x] #3744
• [ ] #3752
• [ ] #3743
• [x] #3742
• [x] #3813
• [x] #3890
• [x] #3814
• [x] #3942
• [x] #3979
• [x] #4020
• [x] #4032
• [x] #4105
• [x] #4170
• [x] #4214
• [x] #4290

Non-Payments changes

• [x] #3740
• [x] #3741
• [x] #3739
• [x] #3754
• [x] #3766
• [x] #3891
• [x] #3957
• [x] #4026
• [x] #4037

Have you spent some time checking if this feature request has been raised before?

• [X] I checked and didn't find a similar issue

Have you read the Contributing Guidelines?

• [X] I have read the Contributing Guidelines

Are you willing to submit a PR?

None