zeroize: move zeroize_derive to toplevel (#1074)

The current directory structure unintentionally packages a copy of
`zeroize_derive` with every copy of `zeroize`.

This commit moves it to the toplevel while making no other changes. This
preserves the commit history.

Author: tarcieri

Cargo.toml

@@ -14,7 +14,7 @@ members = [
     "opaque-debug",
     "wycheproof2blb",
     "zeroize",
-    "zeroize/derive"
+    "zeroize_derive"
 ]
 
 [profile.dev]

zeroize/Cargo.toml

@@ -19,7 +19,7 @@ rust-version = "1.60"
 
 [dependencies]
 serde = { version = "1.0", default-features = false, optional = true }
-zeroize_derive = { version = "1.3", path = "derive", optional = true }
+zeroize_derive = { version = "1.3", path = "../zeroize_derive", optional = true }
 
 [features]
 default = ["alloc"]