Input with eof and no newline bugfix

[tompng]

Fix the bug below

# with readline-ext
$ printf "hello" | ruby -rreadline -e "p Readline.readline('>')"
>hello
"hello"

# with Reline master
$ printf "hello" | ruby -Ilib -rreline -e "p Reline.readline('>')"
>
""

The string "hello" is stored in @continuous_insertion_buffer, need to force input before finishing read.

In some environment (in my M2 Mac), pread raises IOError, so rescue Errno::ESPIPE, IOError change in ansi.rb is needed to test it.

[tompng]

This test was always failing in my local environment.
If sleep on the previous line is too long, close will raise EOFError: end of file reached. If sleep time is too short, assert_screen will fail.
(In my environment, even sleep 0 is too long because start_terminal and close has sleep 0.1 internally. There is no best value. Need to fix yamatanooroti.)

[ima1zumi]

LGTM 🚀