core(fr): always run NetworkUserAgent gatherer

[adamraine]

This was a base artifact in legacy mode but it's a normal artifact in FR.

It wasn't being run because no audits depend on it. This PR avoids the audit dependency filter for this artifact.

[paulirish]

Is this a result of the fact that BaseArtifacts and FRBaseArtifacts are different?

can we align this thing to the types to ensure there arent others slipping through the cracks?

[adamraine]

Is this a result of the fact that BaseArtifacts and FRBaseArtifacts are different?

There is this:

lighthouse/types/artifacts.d.ts

Lines 74 to 90 in d43485b

	/**
	* The set of base artifacts that were replaced by standard gatherers in Fraggle Rock.
	*/
	interface LegacyBaseArtifacts {
	/** The user agent string that Lighthouse used to load the page. Set to the empty string if unknown. */
	NetworkUserAgent: string;
	/** Information on detected tech stacks (e.g. JS libraries) used by the page. */
	Stacks: Artifacts.DetectedStack[];
	/** Parsed version of the page's Web App Manifest, or null if none found. This moved to a regular artifact in Fraggle Rock. */
	WebAppManifest: Artifacts.Manifest | null;
	/** Errors preventing page being installable as PWA. This moved to a regular artifact in Fraggle Rock. */
	InstallabilityErrors: Artifacts.InstallabilityErrors;
	/** A set of page-load traces, keyed by passName. */
	traces: {[passName: string]: Trace};
	/** A set of DevTools debugger protocol records, keyed by passName. */
	devtoolsLogs: {[passName: string]: DevtoolsLog};
	}

But that list includes artifacts that we don't want to be filter resistant (e.g. InstallabilityErrors)

I think this list should include artifacts that are not run in all 3 modes, but should always be run if they can. For example, NetworkUserAgent isn't available in snapshot mode.

Also, looks like HostUserAgent, HostFormFactor and GatherContext don't need to be filter resistant because they are base artifacts.