[Feature Request] Import multiple connections at once

## Description
When sharing connections with someone, it would be useful to be able to import multiple connections in one action.

Today, Graph Explorer can only import a single connection at a time. And immediately after import Graph Explorer tries to connect and sync, which will disable the import button. This forces you to wait for sync to complete, which can take a significant amount of time.

## Preferred Solution
- [ ] Change import file `input` properties to allow multiple selection
- [ ] Don't make the imported connection active to avoid syncing

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