Add project validation to various REST API endpoints.

[mknowlton89]

Features and Changes

As a continuation of #3354 - This PR adds project validation to the Metrics CREATE and UPDATE Rest API Endpoints, as well as the CREATE and UPDATE Environment Rest API endpoints.

Now, if an invalid/non-existent project is passed in, an error will be thrown with a contextual message.

Testing

Experiments

• Pass in a valid project when creating a new experiment and ensure it works as expected
• Pass in a valid project when updating an existing experiment and ensure it works as expected
• Pass in an invalid project id when creating a new experiment and ensure an error is thrown and the experiment is not created
• Pass in an invalid project id when updating an existing experiment and ensure an error is thrown and the experiment is not updated

Metrics

• Pass in a valid projects array when creating a new metric and ensure it works as expected
• Pass in a valid projects array when updating an existing metric and ensure it works as expected
• Pass in an invalid projects array when creating a new metric and ensure an error is thrown and the metric is not created
• Pass in an invalid projects array when updating an existing metric and ensure an error is thrown and the metric is not updated