Change dev_tests configuration options

[Vicky-Goldin]

Description

1. dev_tests.build_type is removed, general.build_type is used instead.
2. dev_tests.build_file is removed, generate.app_build_files is used instead.
3. Added a default value of test for dev_tests.build_targets, since test is commonly used to run tests and generate Jacoco exec file.
4. Before, the values of dev_tests were not validated when loading a toml file (in __validate_config_scope). Now they are validated when running generate or execute, since dev_tests might be used in either of the commands.

Related to #115 from planning repo.

Type of Change

Please check the types of changes your PR introduces.

• [ ] Bug fix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Refactoring (non-breaking code restructuring that preserves functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Build-related update (CI workflow, test cases)
• [ ] Documentation update
• [ ] Other (please describe):

How Has This Been Tested?

Tests pass locally, including tests regarding dev_tests configuration options.

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules