CSharp compiler is incredibly slow in extensions repo

Build times in dotnet/extensions have really been bugging me lately. All these measurements are made on a devbox with 32vCPU | 128GB | 2048GB

For instance:
```
C:\src\dotnet\extensions\src\Libraries\Microsoft.Extensions.AI.Abstractions>dotnet build --no-dependencies -f net8.0 /bl
Microsoft.Extensions.AI.Abstractions net8.0 succeeded (10.1s) → ..\..\..\artifacts\bin\Microsoft.Extensions.AI.Abstractions\Debug\net8.0\Microsoft.Extensions.AI.Abstractions.dll

Build succeeded in 10.6s
```

That's 10 seconds to build a single assembly ( ~10K LOC, 100 files) for a single target framework without any dependencies! Now I can specify /p:SkipAnalyzers=true to avoid this (still 2-4s), but that risks building debt with the code I write that will fail analysis when it comes time to submit.

So I tried to see what was causing it.

Rebuild with
```
dotnet build --no-dependencies -f net8.0 /bl /p:ReportAnalyzer=true
```

Impressive that these can take more time than the build itself. I think that's because it's summing the work across multiple threads.

The biggest culprit is
```
29.868   52      SonarAnalyzer.Rules.CSharp.SymbolicExecutionRunner (S1944, S2053, S2222, S2259, S2583, S2589, S3329, S3655, S3900, S3966, S4158, S5773)
```

I saw we were using an old copy of this analyzer. I upgrade to the latest from NuGet and see the same perf issue. It helped a little, but not completely.
```
C:\src\dotnet\extensions\src\Libraries\Microsoft.Extensions.AI.Abstractions>dotnet build --no-dependencies -f net8.0 /bl /p:ReportAnalyzer=true
Microsoft.Extensions.AI.Abstractions net8.0 succeeded (9.5s) → ..\..\..\artifacts\bin\Microsoft.Extensions.AI.Abstractions\Debug\net8.0\Microsoft.Extensions.AI.Abstractions.dll

Build succeeded in 10.0s
```

That seemed to help a bit:

But still not great. I tried disabling those sonar analyzers completely, but it didn't make a difference (at least after updating them).

I can reduce the time by about 5 seconds but disabling this analyzer:
https://github.com/dotnet/extensions/blob/a2d763f31e2114f0e4c514bef01d9e676d91c1df/src/Libraries/.editorconfig#L497-L500
Which should be fine, since it's `suggestion` anyhow.

The following two are the next up, which gave me another 2s wall clock time:
https://github.com/dotnet/extensions/blob/a2d763f31e2114f0e4c514bef01d9e676d91c1df/src/Libraries/.editorconfig#L945-L948
https://github.com/dotnet/extensions/blob/a2d763f31e2114f0e4c514bef01d9e676d91c1df/src/Libraries/.editorconfig#L328-L331
Those give value though, so I wouldn't really want to disable them.

Some of this seems like simple improvements we can do to improve the dev-time, but I'm still surprised at how bad the perf is even after that. cc @stephentoub @jeffhandley @joperezr