Simplify hazmat feature docs (#1643)

### What
Remove `hazmat` feature from doc cfg attributes, keeping only the
specific `hazmat-address` and `hazmat-crypto` features in documentation.

#### Before
<img width="461" height="214" alt="Screenshot 2025-12-15 at 4 05 12 pm"
src="https://github.com/user-attachments/assets/3e00c4da-cf53-4b34-924f-b8f913bfc1c5"
/>

#### After
<img width="461" height="214" alt="Screenshot 2025-12-15 at 4 05 58 pm"
src="https://github.com/user-attachments/assets/8229806b-22ab-4e76-bd93-aa1f3a57654c"
/>

### Why
The generic `hazmat` feature is used for compilation gating, but really
only exists historically for backwards compatibility and as something
used for testing during development of the SDK. Generally folks should
use the narrower scoped hazmat features, so showing it in documentation
guides folks to do the not best practice, which results in enabling more
hazmat APIs than are necessary.

Author: leighmcculloch

soroban-sdk/src/address.rs

@@ -394,10 +394,7 @@ impl Address {
     /// custom Ed25519 signature verification as a form of authentication
     /// because the master key may not be configured the signer of the account.
     #[cfg(any(test, feature = "hazmat-address"))]
-    #[cfg_attr(
-        feature = "docs",
-        doc(cfg(any(feature = "hazmat", feature = "hazmat-address")))
-    )]
+    #[cfg_attr(feature = "docs", doc(cfg(feature = "hazmat-address")))]
     pub fn to_payload(&self) -> Option<AddressPayload> {
         AddressPayload::from_address(self)
     }
@@ -414,10 +411,7 @@ impl Address {
     /// custom Ed25519 signature verification as a form of authentication
     /// because the master key may not be configured the signer of the account.
     #[cfg(any(test, feature = "hazmat-address"))]
-    #[cfg_attr(
-        feature = "docs",
-        doc(cfg(any(feature = "hazmat", feature = "hazmat-address")))
-    )]
+    #[cfg_attr(feature = "docs", doc(cfg(feature = "hazmat-address")))]
     pub fn from_payload(env: &Env, payload: AddressPayload) -> Address {
         payload.to_address(env)
     }

soroban-sdk/src/address_payload.rs

@@ -1,8 +1,5 @@
 #![cfg(any(test, feature = "hazmat-address"))]
-#![cfg_attr(
-    feature = "docs",
-    doc(cfg(any(feature = "hazmat", feature = "hazmat-address")))
-)]
+#![cfg_attr(feature = "docs", doc(cfg(feature = "hazmat-address")))]
 
 //! Address payload extraction and construction.
 //!

soroban-sdk/src/crypto.rs

@@ -191,10 +191,7 @@ impl Crypto {
 /// incorrectly can introduce security vulnerabilities. Please use [Crypto] if
 /// possible.
 #[cfg_attr(any(test, feature = "hazmat-crypto"), visibility::make(pub))]
-#[cfg_attr(
-    feature = "docs",
-    doc(cfg(any(feature = "hazmat", feature = "hazmat-crypto")))
-)]
+#[cfg_attr(feature = "docs", doc(cfg(feature = "hazmat-crypto")))]
 pub(crate) struct CryptoHazmat {
     env: Env,
 }

soroban-sdk/src/env.rs

@@ -334,10 +334,7 @@ impl Env {
     /// incorrectly can introduce security vulnerabilities. Use [Crypto] if
     /// possible.
     #[cfg_attr(any(test, feature = "hazmat-crypto"), visibility::make(pub))]
-    #[cfg_attr(
-        feature = "docs",
-        doc(cfg(any(feature = "hazmat", feature = "hazmat-crypto")))
-    )]
+    #[cfg_attr(feature = "docs", doc(cfg(feature = "hazmat-crypto")))]
     #[inline(always)]
     pub(crate) fn crypto_hazmat(&self) -> crate::crypto::CryptoHazmat {
         crate::crypto::CryptoHazmat::new(self)