Increase vue slot/link functionality (#5710)

## Summary

Increase functionality for slots and links, covered with playwright
tests.

## Features

- Allow for reroute anchors to work when dragging from input slot
- Allow for dragging existing links from input slot
- Allow for ctrl/command + alt to create new link from input slot
- Allow shift to drag all connected links on output slot
- Connect links with reroutes (only when dragged from vue slot)

## Tests Added

### Playwright

- Dragging input to input drags existing link
- Dropping an input link back on its slot restores the original
connection
- Ctrl+alt drag from an input starts a fresh link
- Should reuse the existing origin when dragging an input link
- Shift-dragging an output with multiple links should drag all links
- Rerouted input drag preview remains anchored to reroute
- Rerouted output shift-drag preview remains anchored to reroute

## Notes

The double rendering system for links being dragged, it works right now,
maybe they can be coalesced later.

Edit: As in the adapter, can be removed in a followup PR

Also, it's known that more features will arrive in smaller PRs, this PR
actually should've been much smaller.

The next ones coming up are drop on canvas support, snap to node, type
compatibility highlighting, and working with subgraphs.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5710-Increase-vue-slot-link-functionality-2756d73d3650814f8995f7782244803b)
by [Unito](https://www.unito.io)

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Co-authored-by: github-actions <[email protected]>

Author: 2 people