Go: SAM: user can run/debug "nested" target=code lambdas

## Problem

Go support was added in Toolkit 1.25, but there is a known limitation:

If a Go handler is defined in `./foo/bar/baz.go` but the manifest is defined in an ancestor directory `/.foo/` , user cannot define a launch config that works.

## Solution

PR: https://github.com/aws/aws-toolkit-vscode/pull/1688

1. Introduce a handler format that encodes the path starting from `projectRoot`
2. Toolkit strips the handler to something supported by `sam`, before invoking `sam build`

## Status

Waiting for feedback from SAM CLI: https://github.com/aws/aws-sam-cli/issues/2844

Start with PR 1688 and the linked SAM CLI issue 2844, then inspect the nested handler case described for ./foo/bar/baz.go and the ancestor manifest in /.foo/. Done means a launch configuration works for this layout and SAM build accepts the handler after the Toolkit transformation.

Written by the indexing model from the issue text.