PARTCON-28: Add INFORMATICA_POWERCENTER connector type

[tanishkhot]

✨ Description

Adds INFORMATICA_POWERCENTER = ("informatica-powercenter", AtlanConnectionCategory.ELT) to AtlanConnectorType, next to the existing IICS entry.

The Informatica PowerCenter connector app creates assets under connection qualified names of the form default/informatica-powercenter/<epoch>. atlan-publish-app derives the category attribute for partial Connections from this enum (PARTIAL_CONNECTION_CATEGORY_BY_CONNECTOR in its constants), so while the slug is missing here those connections get category = "custom" and are skipped by category-based UI surfaces. ELT matches the DBT/Fivetran/Matillion/IICS precedent. The frontend registration for the same slug is already merged (atlan-frontend #30540).

Jira link: https://linear.app/atlan-epd/issue/PARTCON-28/fix-informatica-icon-rendering-for-pc-process-assets

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🧩 Type of change

• 🚀 New feature (non-breaking change that adds functionality)

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✅ How has this been tested?

• AtlanConnectorType.INFORMATICA_POWERCENTER.value → informatica-powercenter, .category.value → elt
• Reverse lookup AtlanConnectorType("informatica-powercenter") resolves to the new member
• pyatlan_v9 picks it up via its from pyatlan.model.enums import * re-export, no second edit needed

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📋 Checklist

• My code follows the project's style guidelines
• I've performed a self-review of my code
• I've added comments in tricky or complex areas (n/a — single enum entry)
• I've updated the documentation as needed (n/a)
• There are no new warnings from my changes
• I've added tests to cover my changes (pure enum entry; follows BLDX-1076: Add GENERIC_OPENLINEAGE connector type and make emit() accept connector_type #908 precedent)
• All new and existing tests pass locally

[linear]

PARTCON-28

[tanishkhot]

CI triage: unit tests/QA are green on all Python versions (3.9-3.13), import-perf and trivy pass. The remaining failures look environmental rather than related to this one-line enum add: the claude check fails in its own setup step (OpenConnect to vpn2.atlan.app returns HTTP 512, twice, and the repo's scheduled scans are failing the same way today), and the integration-test failures are live-tenant state assertions (e.g. admin_test group_count 3 != 2) that an enum entry can't influence.

[Aryamanz29]

lgtm - thanks!