Improve logic for launch configuration executable path

[bkhouri]

Looking at the code base, the extension is making an assumption as to the location of the executables targets location.

See https://github.com/swiftlang/vscode-swift/blob/96192cb6451cae879a929818c458dfd48c524f24/src/debugger/launch.ts#L133-L137

This will fail when the default build system for swift build changes. It would be better to use the --show-bin-path command line option passed to swift build to determine the build output location.

❯ swift build --show-bin-path
/Users/bkhouri/Documents/git/public/swiftlang/swift-package-manager-2/.build/arm64-apple-macosx/debug

❯ swift build --show-bin-path --configuration release
/Users/bkhouri/Documents/git/public/swiftlang/swift-package-manager-2/.build/arm64-apple-macosx/release

❯ swift build --show-bin-path --build-system swiftbuild
/Users/bkhouri/Documents/git/public/swiftlang/swift-package-manager-2/.build/arm64-apple-macosx/Products/Debug

❯ swift build --show-bin-path --build-system swiftbuild  --configuration release
/Users/bkhouri/Documents/git/public/swiftlang/swift-package-manager-2/.build/arm64-apple-macosx/Products/Release


❯ swift build --show-bin-path --configuration release --scratch-path /my-temp
/my-temp/arm64-apple-macosx/release

❯ swift build --show-bin-path --configuration release --scratch-path /my-temp --triple my-triple --build-system swiftbuild
/my-temp/my-triple/Products/Release