Replace FileVersionInfo.GetVersionInfo with DecompilerVersionInfo.Version constant

[MattParkerDev]

Problem

FileVersionInfo.GetVersionInfo requires a path to an assembly on disk. This fails in cases where the assembly has been loaded as a stream, rather than from a file.

Solution

This PR replaces it with Assembly.GetName().Version, which I have verified returns the same string, in my case - "9.1.0.7988".

[siegfriedpammer]

This is a good catch. I wonder why we are using FileVersionInfo in the first place, given that there is DecompilerVersionInfo, which is generated/updated on every build. So there should be no need for FileVersionInfo at runtime nor reflection.

Suggestion:

• You could add public const string FileVersion = Major + "." + Minor + "." + Build + "." + Revision; to DecompilerVersionInfo.template.cs
• Use it in AssemblyInfo.cs and PortablePdbWriter.cs

This would eliminate the need for a file path AND make it AOT-/single-file bundle compatible, since we don't rely on reflection.

[siegfriedpammer]

Addendum: I think, I found another reason for not using reflection: #2691

Seems constructing System.Reflection.AssemblyName involves a lot more than one might think and may cause weird effects.

[MattParkerDev]

Good idea, done! :)