Data retention in LS semantic updater timer

[fm-117]

See Workspace.cs, line 335:

TypeCobol/TypeCobol.LanguageServer/Workspace.cs

Line 335 in 8312290

_semanticUpdaterTimer.Elapsed += (sender, e) => TimerEvent(sender, e, fileCompilerToUpdate);

The lambda expression used for the Elapsed event creates a closure that will capture one instance of FileCompiler. According to memory profiler, this instance is never collected even after document has been closed.

The goal of this issue is to rewrite the semantic updater mechanism so as to ensure that the FileCompiler instance is properly collected.