Tests and documentation for wrong property tags issue

[Abhijeet-Bentley]

imodel-native: iTwin/imodel-native#970

• Added tests for checking behavior of wrong property tags in an ECXml schema.
• Added documentation clearly mentioning what behavior (in this scenario) to be expected across versions.

[naveedkhan8067]

As you have renamed the HandlingUnknownSchemaElements.md, its references should also be updated. For example in IModelDb.md:

From:

To know more about how these unknown elements are handled, refer to [Handling Unknown Schema Elements](./HandlingUnknownSchemaElements.md)

To something like:

To know more about how these unknown elements are handled, refer to [Handling Unknown And Wrong Schema Elements For Newer Versions](./HandlingUnknownAndWrongSchemaElementsForNewerVersions.md)