Upgrade phpstan; increase phpstan level; fix a few bugs

[uuf6429]

• ⚠️ Must be rebased on main after Increase PHPStan level to 9 #58 is merged.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.74%. Comparing base (5a53ec5) to head (602aa24).

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                        Coverage Diff                         @@
##             chore/increase-phpstan-level      #55      +/-   ##
==================================================================
+ Coverage                           87.59%   87.74%   +0.14%     
+ Complexity                            198      197       -1     
==================================================================
  Files                                   1        1              
  Lines                                 508      506       -2     
==================================================================
- Hits                                  445      444       -1     
+ Misses                                 63       62       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[aik099]

What I've mentioned in review-related commens + see my other responses in other comments:

• Upgrade phpstan; increase phpstan level; fix a few bugs #55 (comment)
• Upgrade phpstan; increase phpstan level; fix a few bugs #55 (comment)
• Upgrade phpstan; increase phpstan level; fix a few bugs #55 (comment)

.

[uuf6429]

Anyway, what can we do to make it work? Apparently, we can't rely on the correctness of the php-webdriver/webdriver provided interfaces and need to use its concrete interface implementations, which have extra public methods that we use.

I've made a an attempt in a different branch, but I didn't push it yet since it depends on this one and it would be too complicated to review. Since this is getting a bit complex, I suggest we organise it so:

1. a PR for refactoring/improving webdriver creation (new PR based on your "unrelated changes" comment)
2. a PR for the phpstan upgrade (this current PR)
3. a PR to attempt switching to depending more on interfaces instead of concretions