Issue `FututureWarnings` for deprecated `test_value` machinery

[Dhruvanshu-Joshi]

Description

Added FutureWarnings whenever test_value is accessed and also added pytest.warnings when tests use it.

Related Issue

• [ ] Closes #
• [x] Related to #447

Checklist

• [x] Checked that the pre-commit linting/style checks pass
• [ ] Included tests that prove the fix is effective or that the new feature works
• [x] Added necessary documentation (docstrings and/or example notebooks)
• [x] If you are a pro: each commit corresponds to a relevant logical change

Type of change

• [ ] New feature / enhancement
• [ ] Bug fix
• [ ] Documentation
• [x] Maintenance
• [ ] Other (please specify):