chore: add linter that denies importing math/rand (#6650)

(cherry picked from commit cc84f9e)

Author: mauri870

.golangci.yml

@@ -54,7 +54,8 @@ linters:
     - noctx # noctx finds sending http request without context.Context
     - unconvert # Remove unnecessary type conversions
     - wastedassign # wastedassign finds wasted assignment statements.
-    - gomodguard # check for blocked dependencies
+    - depguard # check for blocked imports from Go files
+    - gomodguard # check for blocked imports from go.mod
     - gomoddirectives
 
 # all available settings of specific linters
@@ -88,9 +89,9 @@ linters-settings:
   goimports:
     local-prefixes: github.com/elastic
 
+  # Check for blocked dependencies in go.mod.
   gomodguard:
     blocked:
-      # List of blocked modules.
       modules:
         # Blocked module.
         - github.com/pkg/errors:
@@ -105,6 +106,15 @@ linters-settings:
               - github.com/gofrs/uuid/v5
             reason: "Use one uuid library consistently across the codebase"
 
+  # Check for blocked imports in Go files.
+  depguard:
+    rules:
+      main:
+        list-mode: lax
+        deny:
+          - pkg: "math/rand$"
+            desc: "superseded by math/rand/v2"
+
   gomoddirectives:
     # Forbid local `replace` directives
     replace-local: false