[ClassLoader] Cast $useIncludePath property to boolean
minor #12371 [ClassLoader] Cast $useIncludePath property to boolean (GeertDD)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #12371).

Discussion
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[ClassLoader] Cast $useIncludePath property to boolean

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
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32001a4 [ClassLoader] Cast $useIncludePath property to boolean