Feature: Add new version API dns (actual)

[vlad-kms]

This set of changes expands the existing Selectel DNS API script dns_selectel.sh to support the Selectel API version v2 (actual).
Now SELECTEL simultaneously works with two versions of the API: legacy DNS API and actual DNS API (new). The goal is to allow SELECTEL users to use the script for two versions.
https://developers.selectel.ru/docs/cloud-services/dns_api/dns_api_actual/

Variables that need to be controlled before starting:
export SL_Ver="v1" -- version API: 'v2' (actual) or 'v1' (legacy).
Default: v2

If SL_Ver is equal "v1", then you need to define the variable
export SL_Key="API_KEY" -- token Selectel (API key)
You can view or create it in the control panel in the upper right corner, open the Profile and Settings menu -> API Keys.
https://my.selectel.ru/profile/apikeys

If SL_Ver is equal "v2", then you need to define the following variables
export SL_Expire=60 -- token lifetime in minutes (0-1440).
Default: 1400 minutes
export SL_Login_ID=<account_id> -- account number in the control panel;
export SL_Project_Name=<project_name> -- name project.
export SL_Login_name= - service user name.
You can view the name in the control panel:
in the upper right corner, open the menu ? Profile and settings ? User management section ? Service users tab
export SL_Pswd='pswd' - The service user password can be viewed when creating a user or changed to a new one.
All these variables will be saved in ~/.acme.sh/account.conf and will be reused as needed.

Tests: https://github.com/vlad-kms/acme.sh/actions
For two versions:
test DNS for v1 (legacy) - for version API DNS legacy
test DNS for v2 (actual) - for version API DNS actual (new)

[github-actions]

Welcome
First thing: don't send PR to the master branch, please send to the dev branch instead.
Please make sure you've read our DNS API Dev Guide and DNS-API-Test.
Then reply on this message, otherwise, your code will not be reviewed or merged.
We look forward to reviewing your Pull request shortly ✨
注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.