libcnb-test: Improve error messages for address_for_port

[edmorley]

Improves the debugging UX for several ContainerContext::address_for_port failure modes.

In particular, if containers crash after startup then the container logs are now included in the panic error message, rather than only the potentially confusing "No public port X published" message from Docker.

Example output with libcnb-test v0.13.0:

thread 'basic' panicked at 'called `Option::unwrap()` on a `None` value', examples/ruby-sample/tests/integration_test.rs:38:63

With libcnb-test from main (that includes #605 and #621):

thread 'basic' panicked at 'Error obtaining container port mapping:

docker command failed with exit code 1!

## stderr:

Error: No public port '12346' published for libcnbtest_tydfxdispzng

## stdout:


', libcnb-test/src/container_context.rs:117:17

After this PR:

thread 'basic' panicked at 'Error obtaining container port mapping:
Error: No public port '12346' published for libcnbtest_giidbduyppom

This normally means that the container crashed. Container logs:

## stderr:

app.rb:1:in `<main>': Example server startup crash error message... (RuntimeError)

## stdout:


', libcnb-test/src/container_context.rs:130:17

Fixes #482.
GUS-W-13966399.