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/

Issue: #5126

For existing installations where only the old version of the API (legacy) is used, nothing will have to be reconfigured and nothing needs to be done for older versions.

Variables that need to be controlled before starting:

export SL_Ver="v1" -- version API: 'v2' (actual) or 'v1' (legacy).
default: v1

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=<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= - 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.