Add xattr-based attribute support to LocalFileSystem

Store object attributes as extended attributes on the local filesystem,
enabling put_opts and put_multipart_opts to persist attributes. Attributes
are set on the staging file before atomic rename to preserve consistency.

- Add xattr dependency (gated by fs feature)
- Map standard attributes to user.* xattr namespace
- Read attributes back in get_opts

Author: Barre

Cargo.toml

@@ -25,7 +25,13 @@ description = "A generic object store interface for uniformly interacting with A
 keywords = ["object", "storage", "cloud"]
 repository = "https://github.com/apache/arrow-rs-object-store"
 rust-version = "1.85"
-include = ["src/**/*.rs", "README.md", "LICENSE.txt", "NOTICE.txt", "Cargo.toml"]
+include = [
+    "src/**/*.rs",
+    "README.md",
+    "LICENSE.txt",
+    "NOTICE.txt",
+    "Cargo.toml",
+]
 
 [package.metadata.docs.rs]
 all-features = true
@@ -46,21 +52,52 @@ url = "2.2"
 walkdir = { version = "2", optional = true }
 
 # Cloud storage support
-base64 = { version = "0.22", default-features = false, features = ["std"], optional = true }
+base64 = { version = "0.22", default-features = false, features = [
+    "std",
+], optional = true }
 form_urlencoded = { version = "1.2", optional = true }
 http-body-util = { version = "0.1.2", optional = true }
-httparse = { version = "1.8.0", default-features = false, features = ["std"], optional = true }
+httparse = { version = "1.8.0", default-features = false, features = [
+    "std",
+], optional = true }
 hyper = { version = "1.2", default-features = false, optional = true }
 md-5 = { version = "0.10.6", default-features = false, optional = true }
-quick-xml = { version = "0.39.0", features = ["serialize", "overlapped-lists"], optional = true }
-rand = { version = "0.9", default-features = false, features = ["std", "std_rng", "thread_rng"], optional = true }
-reqwest = { version = "0.12", default-features = false, features = ["rustls-tls-native-roots", "http2"], optional = true }
-ring = { version = "0.17", default-features = false, features = ["std"], optional = true }
-rustls-pki-types = { version = "1.9", default-features = false, features = ["std"], optional = true }
-serde = { version = "1.0", default-features = false, features = ["derive"], optional = true }
-serde_json = { version = "1.0", default-features = false, features = ["std"], optional = true }
+quick-xml = { version = "0.39.0", features = [
+    "serialize",
+    "overlapped-lists",
+], optional = true }
+rand = { version = "0.9", default-features = false, features = [
+    "std",
+    "std_rng",
+    "thread_rng",
+], optional = true }
+reqwest = { version = "0.12", default-features = false, features = [
+    "rustls-tls-native-roots",
+    "http2",
+], optional = true }
+ring = { version = "0.17", default-features = false, features = [
+    "std",
+], optional = true }
+rustls-pki-types = { version = "1.9", default-features = false, features = [
+    "std",
+], optional = true }
+serde = { version = "1.0", default-features = false, features = [
+    "derive",
+], optional = true }
+serde_json = { version = "1.0", default-features = false, features = [
+    "std",
+], optional = true }
 serde_urlencoded = { version = "0.7", optional = true }
-tokio = { version = "1.29.0", features = ["sync", "macros", "rt", "time", "io-util"] }
+tokio = { version = "1.29.0", features = [
+    "sync",
+    "macros",
+    "rt",
+    "time",
+    "io-util",
+] }
+
+[target.'cfg(target_family="unix")'.dependencies]
+xattr = { version = "1", optional = true }
 
 [target.'cfg(target_family="unix")'.dev-dependencies]
 nix = { version = "0.30.0", features = ["fs"] }
@@ -70,8 +107,22 @@ web-time = { version = "1.1.0" }
 wasm-bindgen-futures = "0.4.18"
 
 [features]
-default = ["fs"]
-cloud = ["serde", "serde_json", "quick-xml", "hyper", "reqwest", "reqwest/stream", "chrono/serde", "base64", "rand", "ring", "http-body-util", "form_urlencoded", "serde_urlencoded"]
+default = ["fs", "xattr"]
+cloud = [
+    "serde",
+    "serde_json",
+    "quick-xml",
+    "hyper",
+    "reqwest",
+    "reqwest/stream",
+    "chrono/serde",
+    "base64",
+    "rand",
+    "ring",
+    "http-body-util",
+    "form_urlencoded",
+    "serde_urlencoded",
+]
 azure = ["cloud", "httparse"]
 fs = ["walkdir"]
 gcp = ["cloud", "rustls-pki-types"]
@@ -105,4 +156,4 @@ features = ["js"]
 [[test]]
 name = "get_range_file"
 path = "tests/get_range_file.rs"
-required-features = ["fs"]
+required-features = ["fs"]