test: update gh_8083, gh_8445 and gh_7434 tests

These tests fail after the commit [1] has been added to the Luatest:

- app-luatest/gh_8083_fatal_signal_handler_test.lua
- app-luatest/gh_8445_crash_during_crash_report_test.lua
- box-luatest/gh_7434_yield_in_on_shutdown_trigger_test.lua

The issue is due to lack of necessary directories:

    sh: 1: cd: can't cd to /tmp/t/001_app-luatest/server-XXX

Just update tests on the simple `fio` module instead `luatest.server`.

[1] tarantool/luatest@7d1358c

NO_CHANGELOG=internal
NO_DOC=internal

(cherry picked from commit 23b61351)