Modernize login

[q1x]

What does this PR do?

This PR modernizes the login function to work with newer versions of Zabbix.

• We now support API token authentication
• Version 5.2 and above renamed user to username in the login method.

What issues does this PR fix or reference?

Fixes:

#1
#2

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

No

Please review Salt's Contributing Guide for best practices.

See GitHub's page on GPG signing for more information about signing commits with GPG.

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 9 lines in your changes missing coverage. Please review.

Project coverage is 62.62%. Comparing base (bc62200) to head (2eb7e14).

Files with missing lines	Patch %	Lines
src/saltext/zabbix/modules/zabbix.py	57.14%	7 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            devel      #12      +/-   ##
==========================================
- Coverage   62.63%   62.62%   -0.02%     
==========================================
  Files          15       15              
  Lines        2703     2721      +18     
  Branches      390      394       +4     
==========================================
+ Hits         1693     1704      +11     
- Misses        892      898       +6     
- Partials      118      119       +1     

Flag	Coverage Δ
Linux	62.62% <57.14%> (-0.02%)	⬇️
macOS	62.58% <57.14%> (-0.01%)	⬇️
project	43.58% <57.14%> (+0.17%)	⬆️
py310	62.58% <57.14%> (-0.01%)	⬇️
py39	62.62% <57.14%> (-0.02%)	⬇️
salt_3006_9	62.62% <57.14%> (-0.02%)	⬇️
salt_3007_1	62.58% <57.14%> (-0.01%)	⬇️
tests	98.93% <ø> (ø)

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