remove payments service from this repo

[kdenhartog]

The payments service has been migrated to a separate repository. I think that means we can now remove it from this repository and clean up or migrate issues over to that repository if they're related to payment service changes.

[clD11]

Just to confirm does this includes all payment related code including nitro:

Nitro

• libs/nitro https://github.com/brave-intl/bat-go/tree/master/libs/nitro
• service/nitro https://github.com/brave-intl/bat-go/blob/master/services/nitro/nitro.go
• nitro-shim https://github.com/brave-intl/bat-go/tree/master/nitro-shim

Payments

• services/payments: https://github.com/brave-intl/bat-go/tree/master/services/payments
• tools/payments: https://github.com/brave-intl/bat-go/tree/master/tools/payments

cc @Sneagan

[clD11]

Got confirmation its okay to remove all of the above #2708 (comment)

cc @DJAndries