Add support for handling cookies (#501)

* add cookie events, command & result references

* add command & result definitions -wip

* rm ref to events

* Reorganize into a new module named "Storage"

* Add storage partition keys to capabilities

* Support cookies with multiple partition keys

* Remove modifications to capabilities processing

* Relocate type definitions

* Implement commands

* Reformat according to document convention

* Rename key in PartitionKey type

* Duplicate field definitions

* Add reminder to editors

* Define type for sameSite value

* Include partition key in response to GetCookies

* Tolerate additional fields

* Include partition key in response to DeleteCookies

* Reference recently-aligned WebDriver concepts

* Require specification of source origin

* Normalize algorithm return type

* Support specification of store w/browsing context

* Correct CDDL errors

* Rename command parameters

* Make "filter" argument optional

* Clarify "get the cookie store" algorithm

* Define a named type for each kind of partition key

* Update index.bs

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

* Update index.bs

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

* Update index.bs

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

* Update index.bs

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

* Update index.bs

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

* Do not infer sourceOrigin; allow UAs to require it

* Correct algorithm names

* Add explanations for userContext and sourceOrigin

* Use a string type

* Incorporate feedback on partition definitions

* Build a new map when expanding partition specifier

* Correct algorithm invocation

* Add guidance on the contents of data structures

* Update index.bs

Co-authored-by: jgraham <james@hoppipolla.co.uk>

* Update index.bs

Co-authored-by: jgraham <james@hoppipolla.co.uk>

* Update index.bs

Co-authored-by: jgraham <james@hoppipolla.co.uk>

* Correct formatting issues

* Correct formatting issue

* Update index.bs

Co-authored-by: Henrik Skupin <mail@hskupin.info>

* Update index.bs

Co-authored-by: Henrik Skupin <mail@hskupin.info>

* Update index.bs

Co-authored-by: Henrik Skupin <mail@hskupin.info>

* Relocate issue reference

* Modify visual presentation of table

* Reference algorithm by its full name

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Co-authored-by: Mike Pennisi <mike@mikepennisi.com>
Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>
Co-authored-by: jgraham <james@hoppipolla.co.uk>
Co-authored-by: Henrik Skupin <mail@hskupin.info>