Support choosing yagna payment platform through goth-config.yml

[kmazurek]

Currently, all settings related to choosing a payment platform in goth tests assume only a single platform to be used at all times. An example implementation of changing the default payment platform (Polygon) is available here: #553

Instead of having a single, hardcoded payment platform it would be valuable if we could choose the desired payment platform through a field in goth-config.yml. Ideally, this should be configurable on a per-node basis (using node-types in the config). I imagine this would be similar to how setting environment variables per node is currently implemented: #505

The choice of payment platforms should be limited to zksync, polygon and erc20 with the relevant environment variables being set for a given yagna node (again, see: #553).