Use skipIfLess helpers like in other test conditions.

Follows #119

In Tarantool, user space ids starts from 512. You can set arbitrary id
or use autoincrement (sequence also starts from 512). Unfortunately,
mixing spaces with autoincremented ids and spaces with explicit ids may
cause id conflict [1]. Since there are cases when we cannot explicitly
set space id (creating a space with SQL), a short range of free ids
(from 512 to 515) causes problems. This patch increases range of free
ids (now it's from 512 to 615) so it should be ok until [1] is resolved.

1. tarantool/tarantool#8036

Part of #215

Set up package paths so queue test instances could be run with arbitrary
work_dir.

Part of #215

Generate tmp work directories for each new Tarantool instance, if not
specified. It prevents possible directory clash issues.

Later `ioutil.TempDir` (deprecated since Go 1.17) must be replaced with
`os.MkdirTemp` (introduced in Go 1.16 as a replacement) when we drop
support of Go 1.16 an older.

Part of #215

Make skip helpers public. Add more wrappers to reduce code duplication.

Part of #215

Support session settings in a separate subpackage "settings" [1]. It
allows to create a specific requests to get or set session
settings. Settings are independent for each connection.

1. https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_space/_session_settings/

Closes #215