Create rule S7431: size_of::<T> should not be used to count elements of type T (#4772)

* Create rule S7431

* Update RSPEC

* Update snippets

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Co-authored-by: yassin-kammoun-sonarsource <yassin-kammoun-sonarsource@users.noreply.github.com>
Co-authored-by: yassin-kammoun-sonarsource <yassin.kammoun@sonarsource.com>

rules/S7431/metadata.json

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+{
+}

rules/S7431/rust/metadata.json

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+{
+  "title": "`size_of::<T>` should not be used to count elements of type `T`",
+  "type": "BUG",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "clippy"
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-7431",
+  "sqKey": "S7431",
+  "scope": "All",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "RELIABILITY": "MEDIUM"
+    },
+    "attribute": "LOGICAL"
+  }
+}

rules/S7431/rust/rule.adoc

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+== Why is this an issue?
+
+Using `size_of::<T>` or `size_of_val::<T>` as a count of elements is misleading because these functions are meant to return the size in bytes, not the count of elements. This can lead to logical errors in the code.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,rust,diff-id=1,diff-type=noncompliant]
+----
+const SIZE: usize = 128;
+let x = [2u8; SIZE];
+let mut y = [2u8; SIZE];
+unsafe { std::ptr::copy_nonoverlapping(x.as_ptr(), y.as_mut_ptr(), std::mem::size_of::<u8>() * SIZE) }; // Noncompliant: uses size_of::<u8>() to determine element count.
+----
+
+==== Compliant solution
+
+[source,rust,diff-id=1,diff-type=compliant]
+----
+const SIZE: usize = 128;
+let x = [2u8; SIZE];
+let mut y = [2u8; SIZE];
+unsafe { std::ptr::copy_nonoverlapping(x.as_ptr(), y.as_mut_ptr(), SIZE) }; // Compliant: uses the actual element count.
+----
+
+== Resources
+=== Documentation
+
+* Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#size_of_in_element_count