fix: Add std feature to serde to fix CI linting issues (#3165)

Author: lucamuscat

opentelemetry-otlp/allowed-external-types.toml

@@ -8,6 +8,9 @@ allowed_external_types = [
     # serde
     "serde::de::Deserialize",
     "serde::ser::Serialize",
+    ## serde: Required for serde version 1.0.222 or greater.
+    "serde_core::de::Deserialize",
+    "serde_core::ser::Serialize",
     # tonic is a pre 1.0 crate
     "tonic::metadata::map::MetadataMap",
     "tonic::transport::channel::tls::ClientTlsConfig",

opentelemetry-proto/Cargo.toml

@@ -58,7 +58,7 @@ prost = { workspace = true, optional = true }
 opentelemetry = { workspace = true }
 opentelemetry_sdk = { workspace = true }
 schemars = { workspace = true, optional = true }
-serde = { workspace = true, optional = true, features = ["serde_derive"] }
+serde = { workspace = true, optional = true, features = ["serde_derive", "std"] }
 serde_json = { workspace = true, optional = true }
 const-hex = { workspace = true, optional = true }
 base64 = { workspace = true, optional = true }