internal/lsp/source: disable fillstruct by default

The discussion on golang/vscode-go#299 has uncovered the fact that
go/printer is very expensive, and we're calling it frequently on file
changes. Analyzers whose suggested fixes require the original file
content are generally posing issues; this is being discussed on
golang/go#40110.

Updates golang/vscode-go#299

Change-Id: I5cb370c9cb508203e463e7243fc781e75876fe30
Reviewed-on: https://go-review.googlesource.com/c/tools/+/241321
Run-TryBot: Rebecca Stambler <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
(cherry picked from commit d5a7453)
Reviewed-on: https://go-review.googlesource.com/c/tools/+/241322

Author: stamblerre

internal/lsp/source/options.go

@@ -632,7 +632,7 @@ func convenienceAnalyzers() map[string]Analyzer {
 	return map[string]Analyzer{
 		fillstruct.Analyzer.Name: {
 			Analyzer: fillstruct.Analyzer,
-			enabled:  true,
+			enabled:  false,
 		},
 	}
 }