cmd/audit: improve performance of versioned formula names

There is a check for other versioned formula with the same name
in the file audit. This just memoizes all of the versioned
formulae in a tap during the first call and then uses that much
shorter list everytime it checks for things.

Library/Homebrew/formula.rb

@@ -489,20 +489,19 @@ def versioned_formula?
     name.include?("@")
   end
 
-  # Returns any `@`-versioned formulae names for any formula (including versioned formulae).
+  # Returns any other `@`-versioned formulae names for any formula (including versioned formulae).
   sig { returns(T::Array[String]) }
   def versioned_formulae_names
     versioned_names = if tap
-      name_prefix = "#{name.gsub(/(@[\d.]+)?$/, "")}@"
-      T.must(tap).formula_names.select do |name|
-        name.start_with?(name_prefix)
-      end
+      name_prefix = name.gsub(/(@[\d.]+)?$/, "")
+      T.must(tap).prefix_to_versioned_formulae_names.fetch(name_prefix, [])
     elsif path.exist?
       Pathname.glob(path.to_s.gsub(/(@[\d.]+)?\.rb$/, "@*.rb"))
               .map { |path| path.basename(".rb").to_s }
+              .sort
     else
       raise "Either tap or path is required to list versioned formulae"
-    end.sort
+    end
 
     versioned_names.reject do |versioned_name|
       versioned_name == name

Library/Homebrew/tap.rb

@@ -644,6 +644,17 @@ def formula_names
     @formula_names ||= formula_files.map(&method(:formula_file_to_name))
   end
 
+  # A hash of all {Formula} name prefixes to versioned {Formula} in this {Tap}.
+  # @private
+  sig { returns(T::Hash[String, T::Array[String]]) }
+  def prefix_to_versioned_formulae_names
+    @prefix_to_versioned_formulae_names ||= formula_names
+                                            .select { |name| name.include?("@") }
+                                            .group_by { |name| name.gsub(/(@[\d.]+)?$/, "") }
+                                            .transform_values(&:sort)
+                                            .freeze
+  end
+
   # An array of all {Cask} tokens of this {Tap}.
   sig { returns(T::Array[String]) }
   def cask_tokens