[py] Add high-level BiDi permissions API

[AutomatedTester]

Introduces a PermissionsManager helper (py/private/_permissions_handlers.py)
that layers convenience methods on top of the existing permissions.setPermission
command, following the same handler-module pattern used for network and script.

Changes

• New _permissions_handlers.py staged into the bidi package by Bazel
• Permissions.__init__ now accepts an optional driver argument (same as Script)
• bidi_enhancements_manifest.py wires up PermissionsManager and exposes the
  convenience methods on the generated Permissions class
• BUILD.bazel adds _permissions_handlers.py to create-bidi-src extra_srcs
• generate_bidi.py extends the driver-arg __init__ to the permissions module
• Unit tests and browser tests for all new methods

New API

# Grant one or more permissions
driver.permissions.grant("geolocation", origin=origin)
driver.permissions.grant(["geolocation", "camera"], origin=origin)

# Deny a permission
driver.permissions.deny("geolocation", origin=origin)

# Reset one, several, or all tracked overrides
driver.permissions.reset("geolocation", origin=origin)
driver.permissions.reset(["geolocation", "camera"], origin=origin)
driver.permissions.reset()  # clears all overrides applied via grant/deny/override

# Temporary override — resets to prompt on exit, even if an exception is raised
with driver.permissions.override("geolocation", "granted", origin=origin):
    ...

API comparison: Selenium BiDi vs. Playwright

Feature	Playwright (BrowserContext)	Selenium BiDi (driver.permissions)
Grant one	grant_permissions(["geolocation"], origin=…)	grant("geolocation", origin=…)
Grant many	grant_permissions(["geo", "camera"], origin=…)	grant(["geo", "camera"], origin=…)
Deny	❌ not supported — denied is the browser default	✅ deny("geolocation", origin=…)
Reset one	❌ only bulk via clear_permissions()	✅ reset("geolocation", origin=…)
Reset many	❌ only bulk	✅ reset(["geolocation", "camera"], origin=…)
Reset all	clear_permissions()	reset() — clears tracked overrides
Temporary override	❌ no context manager	✅ override("geolocation", "granted", origin=…)
Origin scoping	✅ optional origin=	✅ optional origin=
User context scoping	❌ not supported	✅ user_context=
Low-level access	❌ no direct BiDi access	✅ set_permission(descriptor, state, origin)

https://claude.ai/code/session_018zDh8UVeD7rTyJQQZpAVne

[CLAassistant]

All committers have signed the CLA.