How to reproduce:
1. Open any Unity project or create a new one
2. Open Window>Analysis>Profiler
3. Set it to profile Editor instead of Playmode and start recording
4. Create a new script
5. Inspect the spike in CPU Usage

Expected results: Creating a new code file doesn't take as long
Actual results: Creating a code file stalls the Editor and the stall increases with the size of the project

Reproducible with: 2018.4.32f1, 2019.4.21f1, 2020.2.6f1, 2021.1.0b7, 2021.2.0a6

Notes:
1. In 2018.4 instead of SyncVS.PostprocessSyncProject taking a lot of time it's AssetPostProcessingInternal.PostprocessAllAssets()
2. Reproduces when creating any new file that contains code (.cs, .txt and etc.)
3. Reproduces with Rider and VS