test(build-std): Expand existing -Zbuild-std tests

[adamgemmell]

What does this PR try to resolve?

This PR, split off from #16675, adds a series of tests to capture currently untested -Zbuild-std behaviour. It covers:

• Core behaviour like lockfiles and status messages which are at risk of breakage due to recent work which adds builtin packages to the main resolve.
• Some common subcommands - vendor, tree and metadata, at risk for the same reasons.

How to test and review this PR?

This test has no functional changes and just introduces new tests. This PR supports other PRs split off from #16675 by demonstrating that those changes do not change the existing behaviour of -Zbuild-std.

[rustbot]

r? @weihanglo

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Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: @epage, @weihanglo
• @epage, @weihanglo expanded to epage, weihanglo
• Random selection from epage, weihanglo

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.