[dotnet-watch] Possible race condition in GetAggregateCapabilities()

### Describe the bug

`GetAggregateCapabilities` captures current running projects when Roslyn is analyzing the changes being made. When these changes are being applied later on the set of running projects might be different.

### Steps to reproduce

n/a

### Expected behavior

n/a

### Actual behavior

n/a

### Is this a regression?

_No response_

### Are there any workarounds?

_No response_

### dotnet --info output

```console

```

### IDE version

_No response_

### Other details

_No response_