Validate does not allow a single-character subdirectory

[c-suh]

🐛 Describe the bug

Validate tool fails a product if the transfer manifest .tab file has a directory spec with a single-character subdirectory. Very similar to #299.

📜 To Reproduce

Steps to reproduce the behavior:

1. Run validate on the files inside gbo.ast.alcdef-database_v1.0_20211021.zip
2. Read output. Or skip step 1 and read this saved output: gbo.ast.alcdef-database_v1.0_20211021-validate.txt

🕵️ Expected behavior

A directory spec such as '/data/1/' should not cause an error.

📚 Version of Software Used

2.1.0 (but also exists in 2.0.7. Have not tested earlier versions)

🩺 Test Data / Additional context

Actual data available under "To Reproduce". Going by comments from #299 and the pattern shown in the validate report, perhaps adding a star after the first grouping would solve this issue?
Currently: /?([A-Za-z0-9][A-Za-z0-9_-]*[A-Za-z0-9]/?)*
Proposed: /?([A-Za-z0-9]*[A-Za-z0-9_-]*[A-Za-z0-9]/?)*

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🦄 Related requirements

⚙️ Engineering Details

[jordanpadams]

From SR, looks like it will be a little more complicated:

The directory name must not begin or end with a dash or underscore.

[jpl-jengelke]

This passes tests with validate 2.2.0-SNAPSHOT with the error resolved.