Go feature: Modernized go fix

Go 1.26 reimplements the `go fix` command using the same analysis framework as `go vet`, bringing modernization tools from gopls to the command line. The tool now includes 22 analyzers that automatically update code to use newer language features like `any` instead of `interface{}`, `slices.Sort` instead of `sort.Slice`, range-over-int loops, and iterator-based APIs. Unlike `go vet` which reports problems, `go fix` focuses on safe, automated code modernization that doesn't indicate bugs but helps keep codebases current with Go's evolving idioms.