Get rid of legacy names and fields

Created by: mrnugget

After #8008 we don't execute CampaignPlans/CampaignJobs in Sourcegraph anymore. That functionality has been moved to src CLI, which is where it'll stay, even when we move to remote code execution.

With that the names don't make a lot of sense anymore and add a cognitive load to every change we have to make in our system (see https://github.com/sourcegraph/sourcegraph/pull/9073 for an example of how much business logic can be removed if we remove the unused fields).

This will be a breaking change, but since we're still under a feature flag we should do this sooner rather than later.

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• In Go/GraphQL: Remove CampaignPlan.status https://github.com/sourcegraph/sourcegraph/pull/9068
• In Go/schema: Remove CampaignType, Arguments and CanceledAt from CampaignPlan https://github.com/sourcegraph/sourcegraph/pull/9118
• In Go/schema/GraphQL: Rename CampaignPlan to PatchSet
• In Go/schema: Rename CampaignJob to Patch
• In GraphQL: Rename ChangesetPlan to Patch
• Go: See if it's possible to reconcile PatchInput and Patch https://github.com/sourcegraph/sourcegraph/pull/9273
• Update src CLI to work with new names https://github.com/sourcegraph/src-cli/pull/161
• Update frontend to work with new names
• Update documentation https://github.com/sourcegraph/sourcegraph/pull/9235