Use golang.org/x/mod for parsing Fyne version in go.mod

[Jacalz]

Use https://pkg.go.dev/golang.org/x/mod here:

tools/cmd/fyne/internal/commands/build.go

Line 173 in 9efbb19

dependenciesOutput, err := runner.runOutput("mod", "edit", "-json")

[andydotxyz]

Make sure that whatever library we use it supports the new point release notation for Go since 1.21.0

[Jacalz]

I think x/mod is what the compiler uses internally for module parsing. I will be more or less the same as using the Go binary for it.

[andydotxyz]

Yes, but as noted in the issues in golang GitHub the compiler not matching the toolchain/library is the source of problems elsewhere so it felt important to note.