Add cookie filters and partitioned-cookie support: `Delete All Cookies` filters, `Get Cookies urls=`, `Add Cookie partitionKey=`

Use case

Three small parity gaps in the cookie keywords, bundled because they touch the same module:

1. Selective cookie deletion. Deleting just the session cookie while keeping consent/preference cookies is a common pattern (e.g. force a re-login without re-triggering the cookie banner). Today Delete All Cookies is all-or-nothing, so users must Get Cookies, delete everything, and painstakingly re-add the cookies they wanted to keep.

2. URL-filtered cookie retrieval. Get Cookies always returns every cookie in the context. Filtering to the cookies that would actually be sent to a given URL can be approximated in Robot code, but the native filter also applies path/secure/domain matching rules correctly, which hand-rolled filtering usually gets wrong.

3. Partitioned (CHIPS) cookies. As browsers phase out unpartitioned third-party cookies, apps increasingly set cookies with a partition key. There is currently no way to create such a cookie with Add Cookie, and Get Cookies does not show the partition key, so partitioned-cookie behavior cannot be tested at all.

Proposed keyword / arguments

All new arguments are named-only with None defaults (current behavior unchanged when omitted):

• Delete All Cookies *, name=None domain=None path=None — when any filter is given, only matching cookies are removed.
• Get Cookies return_type=dict *, urls=None — urls is a single URL or a list of URLs.
• Add Cookie name value url=None domain=None path=None expires=None httpOnly=None secure=None sameSite=None *, partitionKey=None
• Get Cookies output dicts additionally carry a partitionKey key when present.

*** Test Cases ***
Force Relogin Keeping Consent
    Delete All Cookies    name=session_id
    Reload
    Get Text    h1    ==    Please log in

Assert Cookies Sent To API Host
    ${cookies}=    Get Cookies    urls=https://api.example.com/v1
    Length Should Be    ${cookies}    2

Test Partitioned Third Party Cookie
    Add Cookie    tracker    abc123    url=https://third-party.example
    ...    partitionKey=https://site.example
    ${cookies}=    Get Cookies
    Should Be Equal    ${cookies}[0][partitionKey]    https://site.example

Playwright API

• browserContext.clearCookies — name/domain/path filter options
• browserContext.cookies — urls parameter and partitionKey in returned cookies
• browserContext.addCookies — partitionKey cookie field

Implementation notes

• protobuf/playwright.proto: extend the cookie RPC request messages with the filter fields, urls list, and partitionKey.
• node/playwright-wrapper cookie handlers: pass the options through to clearCookies/cookies/addCookies; include partitionKey in serialized cookie output.
• Browser/keywords/cookie.py: new named-only arguments on the three keywords; docs for each.
• atest: filtered-delete test, urls-filter test; partitionKey round-trip (Chromium supports CHIPS).

Backwards compatibility

Purely additive: all new arguments are named-only and default to None (no filtering / no partition key), and the partitionKey output field is an additive dict key. Existing suites see identical behavior and data.