V3.0.0 Release - Upgrade to .NET 8

[mukunku]

I decided to bump the major version this release since folks need to upgrade to .net 8 (if they don't use the standalone exe which is the majority of users). And it seemed like a good time as any to do so 🤷🏼‍♂️

This PR:

• Upgrades the project to .NET 8 because .NET 7 (and 6) are being retired by the end of this year
• Turns on #nullable enable for the entire solution
• Adds a GitHub Action to run unit tests in PR's
• Cleans up some code and documentation in the repo
• Removes Date Only date formats from the app as they don't seem to be useful
• Help -> About page has a checkbox to create .parquet file association with ParquetViewer now
  • The app will also ask users after they open their 8th parquet file if they'd like to make ParquetViewer their default app for .parquet files if they haven't done so already
• Improves sorting speed & accuracy for Struct, List, Map, and byte[] types
  • Implements IComparable for ListValue, ByteArrayValue, MapValue, StructValue classes so now if you sort a column with one of these fields it will sort fastly and deterministically.
• When a column is sorted, the app will now widen the column to try make sure the sorting arrow is shown
• Struct[] and List<Struct> field type support ([FEAT] Support Array of Struct Type  #108)
• Re-adds sql.execute metrics

[github-actions]

Unit Test Results

✔️ Tests 19 / 19 - passed in 2.5s
🔍 click here for more details

✏️ updated for commit b94c733