Support multiple path syntax for modules; string literal for depends_on

[emdoyle]

Fixes: #483

This allows two new forms in tach.toml configuration:

1. Shorthand for dependencies

• depends_on = [{ path = "module.a"}] can now be written simply as depends_on = ["module.a"]
• the object form is only necessary to specify deprecated = true

2. Shorthand for groups of modules with the same attributes

• modules can now use paths = ["module.a", "module.b"] instead of a single path = "module.a"
• this allows sharing the depends_on, visibility, utility, or unchecked fields across all specified module paths
• it is equivalent to flattening the module definition, but it far more concise