Rename Versioned.getVersion() to getClassVersion()

## 🆕🐥 First Timers Only

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The goal of this issue and all other issues labeled by [**'good first issue'**](https://github.com/issues?q=is%3Aopen+is%3Aissue+org%3Ahashgraph+archived%3Afalse+label%3A%22good+first+issue%22+) is to help you make your first contribution to Hedera.

## 👾 Description of the issue

The interface `com.swirlds.common.io.Versioned` is used in the serialization api. It has a method `int getVersion()` that defines a version of a concrete class for serialization. Since the method name `getVersion()` often collide with downstream naming schemas (like if another interface or abstract class provides a `getVersion()` method) it should be renamed to `getClassVersion()`.

### Proposed Solution:

Refactor the `int getVersion()` method to `int getClassVersion()`.

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## 🤔 Additional Information

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