itest: Add reusable integration test library crate

We were growing too much duplication between projects around
integration tests. Extract a shared helper library that we'll
vendor via git crate dependencies.

Assisted-by: OpenCode (Claude Opus 4.6)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

Cargo.lock

@@ -17,8 +17,10 @@ name = "test-cleanup"
 path = "src/bin/cleanup.rs"
 
 [dependencies]
+itest = { path = "../itest" }
 bcvk = { path = "../kit" }
-color-eyre = { workspace = true }
+anyhow = "1"
+linkme = "0.3"
 dirs = "5.0"
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true }
@@ -29,13 +31,10 @@ serde = { version = "1.0.199", features = ["derive"] }
 serde_json = "1.0.116"
 zlink = "0.4"
 tokio = { version = "1", features = ["rt", "net", "macros"] }
-libtest-mimic = "0.7.3"
 tempfile = "3"
 uuid = { version = "1.18.1", features = ["v4"] }
 camino = "1.1.12"
 regex = "1"
-linkme = "0.3.30"
-paste = "1.0"
 rand = { workspace = true }
 scopeguard = "1"
 cap-std-ext = { workspace = true }