Improve global resolvers for missing keys

[noklam]

NOTE: Kedro datasets are moving from kedro.extras.datasets to a separate kedro-datasets package in
kedro-plugins repository. Any changes to the dataset implementations
should be done by opening a pull request in that repository.

Description

• Refactor the variable nested_key
• remove lambda, use the function, move the default to the underlying function
• Add a test that should fail (passing now)

Currently when access a non-exist global, a default value is return (I believe this is undesired)

Development notes

Checklist

• Read the contributing guidelines
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team

[noklam]

I think we should have a sentinel value NOVALUE rather than None to differentiate a user define default None versus a no-op

${globals: DUMMY_KEY, None} should be different from ${globals: DUMMY_KEY}

[astrojuanlu]

Is this still relevant after merging #2976?

[noklam]

closing in favor or #2976, I discussed with @ankatiyar and the changes are included in the same PR already.