PAB should query node parameters instead of reading from config file

[Brian W Bush]

Describe the feature you'd like

It is fragile and error-prone to have the PAB read the node's protocol parameters from a JSON file when its node connection could be used to query those parameters directly.

Also, not supplying a protocol parameters file results in the PAB using a Data.Default.def value for those, which very well may be inappropriate: https://github.com/input-output-hk/plutus-apps/blob/13836ecf59649ca522471417b07fb095556eb981/plutus-pab/src/Plutus/PAB/App.hs#L271.

Describe alternatives you've considered

Eliminate the pscProtocolParametersJsonPath field of PABServerConfig, and instead query the node directly for its protocol parameters.