This PR adds the check to perform 3-way merge only if datatype
matches to observed state data types else error will be returned.

**Bug Description**:
merge func silently allows to merge when different data types are
provided for 3-way merge and this leads merge data will not match to
expected data. Following is an example:
```go
observed := map[string]interface{}{
	"key1": "value1",
	"key2": "value2",
}

desired := map[string]string{
	"key1": "value1",
	"key2": "value2",
}

got := map[string]interface{}{
	"key1": "value1",
	"key2": "value2",
}
```

Signed-off-by: mittachaitu <[email protected]>

Signed-off-by: mittachaitu <[email protected]>