Fix prompt list size and colorized code line size to match input line size passed to Reline

[tompng]

When you enter 1 and then OPTION+ENTER, rdbg will crash.

[tomoya.ishida:debug]% echo debugger > a.rb
[tomoya.ishida:debug]% rdbg a.rb
[1, 1] in a.rb
=>   1| debugger
=>#0    <main> at a.rb:1
(ruby) 1
#<Thread:0x000000011093fc90@DEBUGGER__::SESSION@server /Users/tomoya.ishida/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/debug-1.8.0/lib/debug/session.rb:179 run> terminated with exception (report_on_exception is true):
/Users/tomoya.ishida/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/reline-0.3.7/lib/reline/line_editor.rb:1131:in `+': TypeError
    from /Users/tomoya.ishida/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/reline-0.3.7/lib/reline/line_editor.rb:1131:in `render_partial'
    from /Users/tomoya.ishida/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/reline-0.3.7/lib/reline/line_editor.rb:498:in `rerender'
    from /Users/tomoya.ishida/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/reline-0.3.7/lib/reline.rb:356:in `block (3 levels) in inner_readline'
...

Fix colorize

Reline requires code.lines.size == output_modifier_proc(code).lines.size. Unless, Reline crashes. I removed chomp from colorize target. This will fix the above bug. chomp was added in #227 to implement RPROMT. RPROMPT is removed in #574 so chomp is no longer needed.

Fix prompt list

If prompt_proc returns few prompt list, it still works because reline interpolates missing prompt. https://github.com/ruby/reline/blob/0f8000443e88ece87ba2f7cd918014c0013995cb/lib/reline/line_editor.rb#L139-L143 But it's better to return prompt list with the same size.