Added JSON input validation for CLI commands

[andrewnester]

Changes

Added JSON input validation for CLI commands. Now when invalid JSON passed as a payload to CLI commands, CLI performs input normalisation and detects if there are any mismatches such as incorrect types, unknown fields and etc.

This diagnostic information is printed in standard error output and does not block command execution, so the change is backward compatible.

This PR also addresses issue when values which are considered "empty" in Go (such as false, 0, "" and etc.) were ignored and not passed to API request payload.

Fixes #1769 #1764 #1625 #1560

Tests

Added unit tests

andrew.nester@HFW9Y94129 ~ % databricks jobs create --json '{"seeti}'
Error: error decoding JSON at (inline):1:2: unexpected EOF


andrew.nester@HFW9Y94129 ~ % databricks jobs create --json '{"seeti": true}'
Warning: unknown field: seeti
  in (inline):1:9

Error: Job settings must be specified.

[pietern]

Could we do the same for the YAML flag?

I believe that's the only reason we still depend on github.com/ghodss/yaml. This package uses the json tags in the types as opposed to yaml tags, which the upstream YAML package uses. Since we use the json tags as well in the dyn package it should be possible to replace it.

Not blocking for this PR, of course.

[pietern]

Thanks, can you TAL at the PR summary before merging?