debugger: proper readline support

Implemented readline history and autocomplete by reusing
readline facilities of Tarantool console. They used to be
being hidden once Lua 'console' module is loaded. With c432e9e9
(lua: don't use public module name as internal one), now they
are available as 'console.lib'.

Closes #7738

NO_TEST=covered by refactored console_debugger_session_test.lua

@TarantoolBot document
Title: proper readline support in readline

Similar to tarantool interactive console, tdbg now uses readline
for its shell. It enables handier input editing, command history
and so on.

(cherry picked from commit 92222451)