Remove references to Grafana-specific schemas in jennies

[K-Phoen]

Jennies currently have some built-in knowledge about the dashboard v1 schema and can generate code specific to it:

• panel/dataquery variant declarations (the VariantConfig() functions)
• dataquery unmarshal
• dataquery identification function (DataqueryType())
• ...

Jennies:

• Go → Go/grafana schema references #689
  • there is still some dataquery-specific code for equality functions
• PHP → Php/grafana schema references #703
• Typescript
• Python → Python - Remove schema-specific codegen #708
• Java