Add 3rd person aliases of Symbol#start_with? and Symbol#end_with?

This is the opposite direction of #39152.

activesupport/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Add 3rd person aliases of `Symbol#start_with?` and `Symbol#end_with?`.
+
+    ```ruby
+    :foo.starts_with?("f") # => true
+    :foo.ends_with?("o")   # => true
+    ```
+
+    *Ryuta Kamizono*
+
 *   Add override of unary plus for `ActiveSupport::Duration`.
 
     `+ 1.second` is now identical to `+1.second` to prevent errors

activesupport/lib/active_support/core_ext/symbol.rb

@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/symbol/starts_ends_with"

activesupport/lib/active_support/core_ext/symbol/starts_ends_with.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class Symbol
+  def start_with?(prefix)
+    to_s.start_with?(prefix)
+  end unless :a.respond_to?(:start_with?)
+
+  def end_with?(suffix)
+    to_s.end_with?(suffix)
+  end unless :a.respond_to?(:end_with?)
+
+  alias :starts_with? :start_with?
+  alias :ends_with? :end_with?
+end

activesupport/test/core_ext/symbol_ext_test.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require_relative "../abstract_unit"
+require "active_support/core_ext/symbol"
+
+class SymbolStartsEndsWithTest < ActiveSupport::TestCase
+  def test_start_end_with
+    s = :hello
+    assert s.start_with?("h")
+    assert s.start_with?("hel")
+    assert_not s.start_with?("el")
+
+    assert s.end_with?("o")
+    assert s.end_with?("lo")
+    assert_not s.end_with?("el")
+  end
+
+  def test_starts_ends_with_alias
+    s = :hello
+    assert s.starts_with?("h")
+    assert s.starts_with?("hel")
+    assert_not s.starts_with?("el")
+
+    assert s.ends_with?("o")
+    assert s.ends_with?("lo")
+    assert_not s.ends_with?("el")
+  end
+end

guides/source/active_support_core_extensions.md

@@ -1758,6 +1758,20 @@ INFO: The three of them return `nil` for blank receivers.
 
 NOTE: Defined in `active_support/core_ext/string/conversions.rb`.
 
+Extensions to `Symbol`
+----------------------
+
+### `starts_with?` and `ends_with?`
+
+Active Support defines 3rd person aliases of `Symbol#start_with?` and `Symbol#end_with?`:
+
+```ruby
+:foo.starts_with?("f") # => true
+:foo.ends_with?("o")   # => true
+```
+
+NOTE: Defined in `active_support/core_ext/symbol/starts_ends_with.rb`.
+
 Extensions to `Numeric`
 -----------------------