[cli] Implement `dagster definitions validate`

[maximearmstrong]

Summary & Motivation

This PR implements dagster definitions validate, a command to validate the definitions of a Dagster project.

---

Expected behavior:

Have a command to validate the definitions of a Dagster project. A behavior similar to Definitions.validate_loadable is expected.

Example:

> dagster definitions validate -f path/to/my/definitions.py

Validating definitions in path/to/my/definitions.py
...

> dagster definitions validate -m my_dagster_project.definitions

Validating definitions in my_dagster_project.definitions.
...

> dagster definitions validate

Validating definitions in ...
...

Input:

Similar to dagster dev as described here - the definitions can be validated:

• from a file, specified as a command line argument, eg. definitions.py
• from a module, specified as a command line argument, eg. my_dagster_project.definitions
• without command line arguments, read from pyproject.toml or workspace.yml.

Output:

Initially as logs in stdout/stderr.

In scope:

• Support the validation of Dagster definitions defined in a Definitions object.
• Implement a behavior similar to Definitions.validate_loadable where the enclosed definitions will be loadable by Dagster:
  • No assets have conflicting keys.
  • No jobs, sensors, or schedules have conflicting names.
  • All asset jobs can be resolved.
  • All resource requirements are satisfied.

Out of scope:

• Support the validation of Dagster definitions defined in a Repository object.
  • See comment here
• Validate definitions dependencies across code locations
  • See thread here
  • Could be added in a next iteration.

Potential improvement and next steps:

• Support usage in CI/CD
• Support output as JSON
• Support definitions constraints
  • eg. Sensors' minimum_interval_seconds should always be of a at least 120 seconds.
• Support validation of definitions with dependencies across code locations.

How I Tested These Changes

Tested locally BK with additional tests