CLI reference, common options: CORS enforced by default + drift fixes

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CORS checks are now enforced by default: document --disable-features cors as the opt-out, and list --experimental-features cors under Deprecated options (still accepted, ignored).

Other drift fixes:

• Add --cors-store-entry-limit and --robot-store-entry-limit
• Add the serviceworker experimental feature (not in help.zon yet)
• Add the Netscape cookies.txt format for --cookie.
• Add run to the commands that accept common options.

[cdebled]

Superseded by #118, which combines the CLI reference updates into one PR.