test: refactor integration tests to assert_cmd and predicates, test all configs in config subdirectory (#1060)

The intention of this PR is to make it easier (more straight forward) to
write `rustic` integration tests by utilizing the `assert_cmd` and
`predicates` crates.

---------

Signed-off-by: simonsan <14062932+simonsan@users.noreply.github.com>

Author: simonsan

Cargo.lock

@@ -91,7 +91,9 @@ self_update = { version = "0.39", default-features = false, optional = true, fea
 
 [dev-dependencies]
 abscissa_core = { version = "0.7.0", default-features = false, features = ["testing"] }
+assert_cmd = "2.0.13"
 dircmp = "0.2"
+predicates = "3.1.0"
 pretty_assertions = "1.4"
 quickcheck = "1"
 quickcheck_macros = "1"
@@ -102,8 +104,6 @@ toml = "0.8"
 
 [target.'cfg(not(windows))'.dependencies]
 libc = "0.2.153"
-
-[workspace.dependencies]
 # cargo-binstall support
 # https://github.com/cargo-bins/cargo-binstall/blob/HEAD/SUPPORT.md
 [package.metadata.binstall]