[dotnet] Sending GeckoDriver output to a log file. (#16081)

* [dotnet] Sending GeckoDriver output to a log file.

Related to #12273

* [dotnet] Running format script

* [dotnet] Adding test for log flag in Firefox

Adding BUILD.bazel to run those tests in CI.

* Update dotnet/src/webdriver/Firefox/FirefoxDriverService.cs

Co-authored-by: qodo-merge-pro[bot] <151058649+qodo-merge-pro[bot]@users.noreply.github.com>

* Update dotnet/src/webdriver/Firefox/FirefoxDriverService.cs

Co-authored-by: qodo-merge-pro[bot] <151058649+qodo-merge-pro[bot]@users.noreply.github.com>

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Co-authored-by: qodo-merge-pro[bot] <151058649+qodo-merge-pro[bot]@users.noreply.github.com>