Remove lowercase transformation in regex validation

[SchernHe]

Description

Resolves #3783

Development notes

• Remove the explicit lower() transformation prior to the regex match
• Add case insensitive flag to project tools regex_validator (as done for example_pipeline)
• Parameterize unit-tests to check for various valid custom regex expressions

Developer Certificate of Origin

We need all contributions to comply with the Developer Certificate of Origin (DCO). All commits must be signed off by including a Signed-off-by line in the commit message. See our wiki for guidance.

If your PR is blocked due to unsigned commits, then you must follow the instructions under "Rebase the branch" on the GitHub Checks page for your PR. This will retroactively add the sign-off to all unsigned commits and allow the DCO check to pass.

Checklist

• Read the contributing guidelines
• Signed off each commit with a Developer Certificate of Origin (DCO)
• 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

[merelcht]

Thanks for the contribution @SchernHe! Can you please add the change to the release notes as well along with your name as contributor under the Community Contributions section?

[merelcht]

Thank you! ⭐

[ankatiyar]

Thanks @SchernHe!