Support for dynamic extension metadata

Currently when Teiid core implements a new translator or customer/user implements a custom translator that has extension metadata, before they can use the translator in Designer to do some modeling, they need to define MED and register it.

With completion of TEIID-2904, in Teiid 8.7, a Admin api method can be used to interrogate the extension metadata properties defined for a translator.

Currently if user uses Teiid Connection importer with any new translator, it ignores all the extension metadata properties and removes them from the returned DDL that Designer did not recognize. That is really bad for custom connectors, because the VDB will not work properly once it is deployed back to Teiid Server.

I propose to devise a way to generate a dynamic MED for the purposes of current metadata import of the source and use it during the import and not ignore those extension metadata properties.

Depending upon implementation detail, we can also read the translators and their extension metadata support during the initial connection time and create all the required MEDs and register them.