x/tools/gopls: support InsertReplaceEdit completion items

[Zyl9393]

What version of Go, VS Code & VS Code Go extension are you using?

Version Information

• Run go version to get version of Go from the VS Code integrated terminal.
  • go version go1.20.1 windows/amd64
• Run gopls -v version to get version of Gopls from the VS Code integrated terminal.
  • v0.12.1
• Run code -v or code-insiders -v to get version of VS Code or VS Code Insiders.
  • 1.79.2
• Check your installed extensions to get the version of the VS Code Go extension
  • v0.39.0
• Run Ctrl+Shift+P (Cmd+Shift+P on Mac OS) > Go: Locate Configured Go Tools command.
  gotests: D:\Projects\Code\Go\bin\gotests.exe (version: v1.6.0 built with go: go1.20.1)
  gomodifytags: D:\Projects\Code\Go\bin\gomodifytags.exe (version: v1.16.0 built with go: go1.20.1)
  impl: D:\Projects\Code\Go\bin\impl.exe (version: v1.1.0 built with go: go1.20.1)
  goplay: D:\Projects\Code\Go\bin\goplay.exe (version: v1.0.0 built with go: go1.20.1)
  dlv: D:\Projects\Code\Go\bin\dlv.exe (version: v1.20.1 built with go: go1.20.1)
  staticcheck: D:\Projects\Code\Go\bin\staticcheck.exe (version: v0.4.2 built with go: go1.20.1)
  gopls: D:\Projects\Code\Go\bin\gopls.exe (version: v0.12.2 built with go: go1.20.1)

Share the Go related settings you have added/edited

    "go.useLanguageServer": true,
    "go.lintOnSave": "off",

Describe the bug

VsCode setting "editor.suggest.insertMode": "insert" has no effect in Go code.

Steps to reproduce the behavior:

1. Write some code:

package main

import "fmt"

type Sword struct {
	Blade
	Hilt
}

type Blade struct {
	Length    float64
	Sharpness float64
}

type Hilt struct {
	Girth float64
}

func main() {
	fmt.Println(Sword{Blade: Blade{Length: 0.8, Sharpness: 0.7}})
}

2. On the line fmt.Println(Sword{Blade: Blade{Length: 0.8, Sharpness: 0.7}}), place cursor in front of the first occurrence of Blade.
3. Type Hi to trigger autocompletion.
4. Choose Hilt from the suggestions.
5. Blade is replaced by Hilt yielding fmt.Println(Sword{Hilt: Blade{Length: 0.8, Sharpness: 0.7}}) instead of fmt.Println(Sword{HiltBlade: Blade{Length: 0.8, Sharpness: 0.7}}).

[hyangah]

Gopls does not yet support InsertReplaceEdit feature (available from LSP3.16).
@findleyr Do you want to move this to the gopls issue tracker as a feature request?

[findleyr]

We should definitely support this; it's a pain point I run into frequently.

Transferring.

[gopherbot]

Change https://go.dev/cl/585275 mentions this issue: gopls/internal/server: support InsertReplaceEdit completion

[gopherbot]

Change https://go.dev/cl/587135 mentions this issue: gopls/internal/protocol: customize InsertReplaceEdit JSON unmarshal