Update per W3C spec. Pruning legacy cruft.

[robocoder]

The 2.0 release will mark the start of "W3C First" support. IOW the client will default to W3C WebDriver Protocol, and where possible, provide some fallback for legacy JSON Wire Protocol.

CompatBusters:

• Bumped PHP requirement to PHP 7.2 or above
• CI - dropped Selenium 2.53.1 and 3.141.59 from the test matrix
• Dropped WebDriverInterface, ClassLoader, Ime, Log, LogType, Storage, and Touch classes
• Dropped SauceLabs Capabilities (and incomplete REST API support)
• Pruned the Exception classes

Maintenance:

• Updated to W3C WebDriver Working Draft: 14 November 2023

Features:

• added Extensions for ChromeDevTools, Selenium Extensions, Federated Credential Management API, and Web Authentication
• added low-level Actions builder and related input source classes
• added Alert, Execute, Platform, Proxy, ProxyType, and Shadow classes