Create rule S3723: Array elements should be separated by commas (#4688)

* Add rust to rule S3723

* Update RSPEC

* Remove tag

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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/S3723/rust/metadata.json

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+{
+  "title": "Array elements should be separated by commas",
+  "type": "CODE_SMELL",
+  "code": {
+    "impacts": {
+      "MAINTAINABILITY": "MEDIUM"
+    },
+    "attribute": "FORMATTED"
+  },
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "2min"
+  },
+  "tags": [
+    "clippy"
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-3723",
+  "sqKey": "S3723",
+  "scope": "All",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown"
+}

rules/S3723/rust/rule.adoc

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+== Why is this an issue?
+
+When defining arrays in Rust, it is possible to forget a comma between elements, especially when the elements are binary operator expressions that span multiple lines. This can lead to unexpected results, causing logical errors or runtime issues.
+
+The origin of this problem is often due to oversight or formatting changes that split expressions across lines without adding the necessary comma.
+
+== How to fix it
+
+To fix this issue, add commas after each element or write the entire array on a single line.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,rust,diff-id=1,diff-type=noncompliant]
+----
+let a = &[
+    -1, -2, -3 // Noncompliant: <= no comma here
+    -4, -5, -6
+];
+----
+
+==== Compliant solution
+
+[source,rust,diff-id=1,diff-type=compliant]
+----
+let a = &[
+    -1, -2, -3,
+    -4, -5, -6,
+];
+----
+
+== Resources
+=== Documentation
+
+* Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#possible_missing_comma