feat(openebs): poolname input validation (#21277)

**Description**
Adds input validation to the poolname / dataset variable to prevent
users entering common invalid paths
- rejects leading `/`
- enforces at least one `/`
- rejects backslash `\` in the path
- rejects `ix-applications` in the path
- rejects `TANK` or `TANK/` entries

⚒️ Fixes  #21275 

**⚙️ Type of change**

- [x ] ⚙️ Feature/App addition
- [ ] 🪛 Bugfix
- [ ] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] 🔃 Refactor of current code

**🧪 How Has This Been Tested?**
Tested via https://regex101.com/r/8aNdeE/1

**📃 Notes:**
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**✔️ Checklist:**

- [x ] ⚖️ My code follows the style guidelines of this project
- [x ] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [ ] 📄 I have made corresponding changes to the documentation
- [ ] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [x ] ⬆️ I increased versions for any altered app according to semantic
versioning
- [ x] I made sure the title starts with `feat(chart-name):`,
`fix(chart-name):` or `chore(chart-name):`

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

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charts/system/openebs/Chart.yaml

@@ -56,4 +56,4 @@ sources:
   - https://github.com/truecharts/charts/tree/master/charts/system/openebs
   - https://github.com/truecharts/containers/tree/master/apps/scratch
 type: application
-version: 4.3.11
+version: 4.3.12

charts/system/openebs/questions.yaml

@@ -104,6 +104,7 @@ questions:
                       schema:
                         type: string
                         default: ""
+                        valid_chars: '^(?!.*\\)(?!.*ix-applications)[^\/]+(\/[^\/]+)+$'
                         required: true
                     - variable: fstype
                       label: "fstype"