cli: reusable code generation

[hgiasac]

• Support embedded fields.
• If neither function nor procedure is generated, your project may use Go workspace. In this case, the CLI will print a warning to ask you to add the submodule path to the go.work file.
• Move logs of /health and /metrics endpoints to the debug level
• Make code generation reusable for other connector libraries:
  • Support the snake_case naming style for operation names via the --style=snake-case argument.
  • Generate the connector schema to Go code via the --schema-format=go argument.
  • Generate handlers in the same package as defined functions. The connector.generated.go file simply imports those handlers to execute the logic.
  • Add a new --type-only argument to skip generating the connector.generated.go file. Connector authors can customize the connector codes as they wish.

[github-actions]

Package	Line Rate	Health
github.com/hasura/ndc-sdk-go/cmd/hasura-ndc-go/command/internal	83%	✔
github.com/hasura/ndc-sdk-go/cmd/hasura-ndc-go/command	41%	➖
github.com/hasura/ndc-sdk-go/cmd/hasura-ndc-go/version	43%	➖
github.com/hasura/ndc-sdk-go/connector	52%	➖
github.com/hasura/ndc-sdk-go/example/reference	65%	➖
github.com/hasura/ndc-sdk-go/internal	53%	➖
github.com/hasura/ndc-sdk-go/scalar	98%	✔
github.com/hasura/ndc-sdk-go/schema	50%	➖
github.com/hasura/ndc-sdk-go/utils	30%	❌
Summary	54% (5921 / 10973)	➖

Minimum allowed line rate is 40%