Add historical versions of voltageRegulation xsd for compatibility purposes

Please check if the PR fulfills these requirements

[X] The commit message follows our guidelines
[X] Tests for the changes have been added (for bug fixes / features)
[ ] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem?

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

"Historical" versions of the VoltageRegulation extension are not supported.

What is the new behavior (if this is a feature change)? "Historical" versions of the VoltageRegulation extension are supported.

Does this PR introduce a breaking change or deprecate an API?

[ ] Yes
[X] No

If yes, please check if the following requirements are fulfilled

[ ] The Breaking Change or Deprecated label has been added
[ ] The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

Other information:

The VoltageRegulation extension was historically a private extension which was added to powsybl-core. When it was private, the extension version was increased with each IIDM versions (from 1.0 to 1.12) but versions from 1.1 to 1.12 were identical. When released in powsybl-core these duplicates were not created. But since there is no clean mechanism to match historical versions to the powsybl-core versions, reading serialized network with an historical version is not possible. This PR introduces these historical versions for compatibility.

The default version when serializing has not changed and is still 1.1 for IIDM >= 1.2.

powsybl / powsybl-core

Add historical versions of voltageRegulation xsd for compatibility purposes #3083

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