Improve signatures of IO#<<, IO#advise, IO#autoclose=, IO#autoclose?

[ybiquitous]

This change does the following for some methods of the IO class:

• add missing documents
• add tests
• make some types more accurate

See the API doc: https://ruby-doc.org/core-3.0.0/IO.html

[ybiquitous]

[note] Note that the argument type changes from boolish to bool. Because io.autoclose = "yes" returns "yes" for example.

We can confirm this behavior as follows:

  def test_autoclose=
    IO.open(IO.sysopen(__FILE__)) do |io|
      assert_send_type "(String) -> bool",
                       io, :autoclose=, "yes"
    end
  end

$ bundle exec ruby test/stdlib/IO_test.rb
...
Failure: test_autoclose=(IOInstanceTest):
  Call trace does not match with given method type: #<struct RBS::Test::CallTrace method_name=:autoclose=, method_call=#<RBS::Test::ArgumentsReturn:0x00007fa2aea9ac38 @arguments=["yes"], @exit_value="yes", @exit_type=:return>, block_calls=[], block_given=false>.
  <["[IOautoclose=] ReturnTypeError: expected `bool` but returns `\"yes\"`"]> was expected to be empty.
/Users/masafumi.koba/git/ybiquitous/rbs/test/stdlib/test_helper.rb:240:in `assert_send_type'
test/stdlib/IO_test.rb:129:in `block in test_autoclose='
     126:
     127:   def test_autoclose=
     128:     IO.open(IO.sysopen(__FILE__)) do |io|
  => 129:       assert_send_type "(String) -> bool",
     130:                        io, :autoclose=, "yes"
     131:     end
     132:   end
test/stdlib/IO_test.rb:128:in `open'
test/stdlib/IO_test.rb:128:in `test_autoclose='
...

[ybiquitous]

I believe the following Sider issue is closeable:
https://sider.review/gh/repos/174796313/pulls/571#issue-5289513

[ybiquitous]

[Goodcheck] Prefer boolish over bool for method arguments and block return values (view)

See the doc below:
https://github.com/ruby/rbs/blob/78d04a2db0f1c4925d2b13c2939868edf9465d6c/docs/syntax.md#bool-or-boolish

Rule
rbs.prefer_boolish

You can close this issue if no need to fix it. Learn more.

See #571 (comment)

[soutaro]

Thanks! 🎉