Add Ext IBM iSeries Definition.

[LouwMarais]

Relevant information

Added a new External IBM iSeries entity definition with the main goal being that our custom insights metric generated with an attribute of includeInIseriesEntity should be used to automatically create our IBM iSeries as an Entity and visible on distributed tracing maps

Checklist

• I've read the guidelines and understand the acceptance criteria.
• The value of the attribute marked as identifier will be unique and valid.
• I've confirmed that my entity type wasn't already defined. If it is I'm providing an explanation above.

[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ LouwMarais
❌ jmarais

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[LouwMarais]

I am going to have to start this pull request over. somehow got my wrong username on the commit and cannot do the CLA

[LouwMarais]

updated pr is here: #1895