feat: Add all deprecated transformations

[benjackwhite]

Problem

We don't want to offer these in the UI but we do want to be able to work with them when we migrate plugins over. This is all used plugins on the US.

Changes

• Adds them in as non-modified a way as possible
• Also includes geoip as I figured it may be easier to do the migration this way for everything and then follow up after

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Does this work well for both Cloud and self-hosted?

How did you test this code?

[greptile-apps]

PR Summary

This PR adds several deprecated transformation plugins to the PostHog plugin server to support plugin migration. Here's a concise summary of the key changes:

• Added LegacyPluginExecutorService to handle deprecated transformations with GeoIP functionality through hub.mmdb service
• Implemented various transformation plugins including GeoIP, URL normalization, event deduplication, and property filtering
• Added comprehensive test coverage for each plugin including edge cases and error scenarios
• Removed metadata imports from plugins and consolidated plugin type definitions
• Added test helpers for GeoLite2 City database testing

Key points to review:

• Several plugins have potential issues with error handling and input validation that should be addressed
• Some plugins are marked as 'alpha' status despite being deprecated, which could be confusing
• The GeoIP functionality appears in both deprecated and active plugins, potential for conflicts
• Direct mutation of event objects in some plugins could cause side effects
• Some plugins lack proper documentation about transformation purposes and edge cases

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