SolaceIO.Write: add data classes, connector interface

[iht]

This is a followup PR to #31906, and part of the issue #31905

This adds the interface of the Write connector and a few classes (data classes, POutput) that are used by the connector.

More changes are coming in a subsequent PR.

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[iht]

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[shunping]

Code change looks good.

Are we expecting unit and integration tests to come in the follow-up PR?

[iht]

@shunping Yes, integration tests, and the actual code of the connector are prepared in an upcoming PR. I am sending them in "chunks" because it is thousands of lines of code, to facilitate the review.

[Abacn]

merge this after received a lgtm review above