Modify and consume the new consolidated config file format with updated `data-source` section

[Aniruddh25]

As per the rfc #935, we need to move the cosmos specific section which today is here:

data-api-builder/ConfigGenerators/dab-config.cosmos.reference.json

Line 7 in ff2beff

"cosmos": {

to the options property under the data-source section:

{
  "$schema": "dab.draft-01.schema.json",
  "data-source": {
    "database-type": "cosmos",
    "options": {
      "database": "",
       "schema": ""
    },
    "connection-string": "AccountEndpoint=https://localhost:8081/;AccountKey=REPLACEME;"
  }
}