Add Playwright driver (no deps)

[ftes]

Add Playwright test driver. It communicates with the playwright node.js server via a Port. No additional dependencies.

Details

• bump to elixir 1.18 to use parameterized ExUnit tests (run live/static tests also with playwright)
• add minimal playwright protocol (communicate with playwright node.js server via Port)
• add `PhoenixTest.Playwright driver (very close to feature parity, some known inconsistencies that are documented via tests)
• add PhoenixTest.Case to allow easily switching drivers via @tag :playwright
• add optional deps ecto + postgres to test sandboxing of concurrent browser tests

Out of scope (just document how to)

• installing: nodejs, npm package playwright, playwright browser(s)

[ftes]

In my eyes this is the most promising approach of the three so far (#136 , #74 #145).

The amount of code required to interface with playwright via a Port is fairly small. And this gives us the flexibility to tailor the exact behaviour to PhoenixTest.

@germsvel If you have time I'd appreciate hearing your thoughts.

[ftes]

New Idea: Performant assertions + helpful and consistent error messages in case of failure:

Happy path (test succeeds): Assert using playwright primitives. Test fails: Generate error by calling PhoenixTest.Assertions or PhoenixTest.Element.*.find* function.

[ftes]

Replaced also_test_js macro with ExUnit 1.18 parameterized tests. As a side effect, playwright tests only run for the CI test matrix elixir=main1.18 (1.18) entry. And not for the older versions.

Given this would be a driver in "beta" state anyway, I think that's fine.