Debugger followup: fix breakpoint for relative path

In debugger step 2 brand new breakpoints there is an issue of setting bp for the outer and current dirs (i.e. ../ and ./). The breakpoint is set, but during runtime the hook isn't activated. Consider the example:

luadebug.lua: Loaded for 2.11.0-entrypoint-999-g0241645fd
break via dbg() => ./main.lua:8 in chunk at ./main.lua:0
   5   
   6   dbg()
   7   
   8=> hello_1()
   9   hello_2()
  10   
  11   local compat = require('tarantool').compat
luadebug.lua> b ../build/main.lua:11
Added breakpoint ../build/main.lua:11.
   8   hello_1()
   9   hello_2()
  10   
  11=>●local compat = require('tarantool').compat
  12   
  13   print(compat.dump())
luadebug.lua> c
hello 1!
hello 2!
require('tarantool').compat({
    yaml_pretty_multiline            = 'default',
    json_escape_forward_slash        = 'default',
    fiber_channel_close_mode         = 'default',
    box_cfg_replication_sync_timeout = 'default',
})

Start with the debugger step 2 changes referenced in pull request 7790 and reproduce the example in luadebug.lua using breakpoints for ./main.lua and ../build/main.lua. Trace why the runtime hook is not activated for these relative paths; done means both outer- and current-directory breakpoints activate during execution.