optimize internal gix usage for faster compile time

Even though there is a chance that overall, it will compile multiple
different versions of the same thing so it's not actually faster.

But let's not think too much about that.

Author: Byron

gix-config/tests/Cargo.toml

@@ -17,7 +17,7 @@ path = "config.rs"
 [dev-dependencies]
 gix-config = { path = ".."}
 gix-testtools = { path = "../../tests/tools"}
-gix = { path = "../../gix" }
+gix = { path = "../../gix", default-features = false }
 gix-ref = { path = "../../gix-ref" }
 gix-path = { path = "../../gix-path" }
 gix-sec = { path = "../../gix-sec" }

gix-index/tests/Cargo.toml

@@ -20,7 +20,7 @@ gix-features-parallel = ["gix-features/parallel"]
 gix-index = { path = ".." }
 gix-features = { path = "../../gix-features", features = ["rustsha1", "progress"] }
 gix-testtools = { path = "../../tests/tools"}
-gix = { path = "../../gix"}
+gix = { path = "../../gix", default-features = false, features = ["index"] }
 gix-hash = { path = "../../gix-hash"}
 filetime = "0.2.15"
 bstr = { version = "1.3.0", default-features = false }