Oro 6.0.x compatibility added

[OleksandrProtsiuk]

This PR can be used as a starting point for the extension upgrade.
Most of the changes were done automatically with the upgrade-toolkit tool.

Here is a short list of done changes:

• Updated requirements to oro/commerce 6.0.*
• oro/upgrade-toolkit automatic migrations applied

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	yes/no

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