test(iroh-cli): Improve bao_store_migration test logging

[matheus23]

Description

We didn't get good logs on the cli_bao_store_migration test so far. Here's what it's output was in a failure case:

--- STDOUT:              iroh-cli::cli cli_bao_store_migration ---

running 1 test
|Iroh is running
|Node ID: cnzuojj4sbo2ulpqoo2riyrdsn2j4pnp3b5bgrjubsft72nutlca
iroh started up.
test cli_bao_store_migration ... FAILED

failures:

failures:
    cli_bao_store_migration

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 12 filtered out; finished in 2.71s


--- STDERR:              iroh-cli::cli cli_bao_store_migration ---
thread 'cli_bao_store_migration' panicked at iroh-cli/tests/cli.rs:394:5:
assertion `left == right` failed
  left: ""
 right: "4yny3v7anmzzsajv2amm3nxpqd2owfw4dqnjwq6anv7nj2djmt2q (0 B)\n"

This was only capturing stdout from one of the four iroh commands.

This PR changes that. Now stdout and stderr are captured by all iroh commands in the cli_bao_store_migration test.

Breaking Changes

None

Notes & open questions

I've also switched PathBuf::to_string_lossy() calls to be PathBuf::display() calls.

Change checklist

• Self-review.
• [ ] Documentation updates following the style guide, if relevant.
• [ ] Tests if relevant.
• [ ] All breaking changes documented.