Metadata copying method does not retain existing metadata

## Describe the bug
This method should not replace the metadata, but merge metadata from 2 schemas:
```scala
val schemaMerged = SparkUtils.copyMetadata(schemaFrom, schemaTo)
```

## Code snippet that caused the issue
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## Expected behavior
Metadata copying method should retain existing metadata.

## Context
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## Copybook (if possible)
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