tools: use `go install` to install tools with go1.18

[hyangah]

Tools used by vscode-go are installed using go get - with Go 1.18, go get won't build or install binaries.
See golang/go#43684 for details.

This extension and containers that set up environments for this extension need to be updated prior to Go 1.18 release.

• Update installTool to change the installation method based on users' Go version. CL 355974
• Update github workflows
• Update kokoro builder workflow

[gopherbot]

Change https://golang.org/cl/355974 mentions this issue: src/goInstallTools: use go install for go1.16+

[gopherbot]

Change https://golang.org/cl/359397 mentions this issue: tools/installtools: add a helper to install Go tools for testing

[hyangah]

will ping cloud shell and github codespaces team once go1.18 rc is cut.