align the output of vars with 'expresson' spec

Please answer the following before submitting your issue:

Note: Please include any substantial examples (debug session output,
stacktraces, etc) as linked gists.

If this is about source listing not showing up (or breakpoints not being
accepted) while running in a container please read our
[FAQ](https://github.com/go-delve/delve/blob/master/Documentation/faq.md#substpath)
first.

1. What version of Delve are you using (`dlv version`)?

Delve Debugger
Version: 1.23.0
Build: $Id: e673f2da02185a1c2b6dea52842b0a8c7e7a03b9 $

3. What version of Go are you using? (`go version`)?

go version go1.20.14 linux/amd64

5. What operating system and processor architecture are you using?

linux/amd64

7. What did you do?

% build a helloword case, with debug enabled
% lauch "dlv exec ./hello"
% run and break, then execute "vars" command
% pick up a variable to print, say "print internal/bytealg.MaxLen"

9. What did you expect to see?

Suggest "vars" outputs variable expressions in the format that "print" recognizes, as https://github.com/go-delve/delve/blob/master/Documentation/cli/expr.md#specifying-package-paths defines.

Take internal/bytealg.MaxLen as an example, "internal/bytealg".MaxLen might be better.

11. What did you see instead?

Start with the Delve `vars` command and compare its output with the expression syntax described in Documentation/cli/expr.md under “Specifying package paths.” Use `internal/bytealg.MaxLen` as the example; done means the displayed expression is accepted by the `print` command.

Written by the indexing model from the issue text.