Removing MYSQL_PWD variable from MauticMysqlTestCase

[JonasLudwig1998]

Q	A
Bug fix? (use the a.b branch)	✔️
New feature/enhancement? (use the a.x branch)	❌
Deprecations?	❌
BC breaks? (use the c.x branch)	❌
Automated tests included?	❌
Related user documentation PR URL	mautic/user-documentation#...
Related developer documentation PR URL	mautic/developer-documentation-new#...
Issue(s) addressed	Fixes #...

Description

Seems like with the most recent ddev version, functional tests are not working properly when trying to access the database. The following error will show up:
Exception: mysqldump --opt -h"${:db_host}" -P"${:db_port}" -u"${:db_user}" "${:db_name}" > "${:db_backup_file}" failed with status code 2 and last line of "mysqldump: Got error: 1045: "Access denied for user 'db'@'...' (using password: YES)" when trying to connect

Seems like the problem is occurs due to the MYSQL_PWD variable which isn't accepted anymore. I solved the problem by changing the variable to db_host.

---

📋 Steps to test this PR:

1. Open this PR on Gitpod or pull down for testing locally (see docs on testing PRs here)
2. Run an existing functions test (e.g. composer test -- --filter testManipulatorSetOnCampaignTriggerAction)
3. See that it will run without an error

[shinde-rahul]

Thanks for the PR!

Quick note: when running the tests locally with DDEV (which defaults to MariaDB), the current mysql* command fails because MariaDB doesn’t support MYSQL_PWD. This results in an 'Access denied' error.

The changes work reliably across both MariaDB and MySQL, avoiding test failures in local environments.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.70%. Comparing base (a67d47e) to head (565ce8e).
Report is 4 commits behind head on 5.2.

Additional details and impacted files

@@            Coverage Diff            @@
##                5.2   #15067   +/-   ##
=========================================
  Coverage     63.70%   63.70%           
- Complexity    34683    34684    +1     
=========================================
  Files          2274     2274           
  Lines        103770   103771    +1     
=========================================
+ Hits          66110    66111    +1     
  Misses        37660    37660           

see 1 file with indirect coverage changes

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[JonasLudwig1998]

@shinde-rahul I had to do some further adjustments because there were problems in the ci workflow when running mautic with mariadb.

The new changes work. But I'm not sure if I really found the best solution. Are there any security issues that could come with the new changes?