Add test-only dependencies; automatically include required test depen…

…dencies

It saves time and binary size not to include dependencies only needed
for tests to the assembled output jar. This commit adds a
`[test.dependencies]` section to `Kargo.toml` that can be used to
specify test-only dependencies.

The required test-only dependencies for running and annotating tests are
now included automatically and don't need to be listed in Kargo.toml for
every project.

Test plan:
- `kargo test`

Fix a bug in constructing the path for running

Because (+) is overloaded, we were accidentally adding the segments of
the built jar file's path to the claspath, rather than the full path.

Update README for test command, run

Fix an issue with quoted config keys

Update README for run command

Update README.md