feat: Install an unlinked formula via brew install if --overwrite is passed

If the intention is to overwrite any existing links, then `brew install` should go on to install over an unlinked formula

Library/Homebrew/cmd/install.rb

@@ -289,6 +289,7 @@ module Homebrew
             only_dependencies: args.only_dependencies?,
             force:             args.force?,
             quiet:             args.quiet?,
+            overwrite:         args.overwrite?,
           )
         end
 

Library/Homebrew/install.rb

@@ -60,7 +60,8 @@ module Homebrew
         fetch_head: false,
         only_dependencies: false,
         force: false,
-        quiet: false
+        quiet: false,
+        overwrite: false
       )
         # head-only without --HEAD is an error
         if !head && formula.stable.nil?
@@ -132,7 +133,7 @@ module Homebrew
                 The currently linked version is: #{formula.linked_version}
               EOS
             end
-          elsif only_dependencies
+          elsif only_dependencies || (!formula.linked? && overwrite)
             msg = nil
             return true
           elsif !formula.linked? || formula.keg_only?