Add metadata env method to provider context

[jared-rimmer]

resolves #5522

Description

• Added the method dbt_metadata_envs which is a wrapper for the get_metadata_env method which is imported from dbt.contracts as it already contained the required functionality.
• Also includes small refactoring of the tests to add two helper functions for parsing json logs and find the result needed in the parsed logs. This was repeated in another test so decided to split it out to avoid repetition.

Open Question

• The requirements on the initial issue mention the DBT_CLOUD variables which are detailed here. Are you happy for me to extend the dbt_metadata_envs method to search for the prefix DBT_CLOUD_ as well?

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[gshank]

You need to run "changie new" to create a changelog entry. See CONTRIBUTING.md

[smitsrr]

@gshank - any other changes required on this PR?

[gshank]

I think if you merge main into your branch, this is probably ready to go. There were some metrics attribute name changes so tests are failing.

[jared-rimmer]

All done @gshank