fix: ensure the web UI doesn't break when license telemetry required check fails (#16667)

Addresses https://github.com/coder/coder/issues/16455.

## Changes

- Initialize default entitlements in a Set to include all features
- Initialize entitlements' `Warnings` and `Errors` fields to arrays
rather than `nil`s.
- Minor changes in formatting on the frontend

## Reasoning

I had to change how entitlements are initialized to match the `codersdk`
[generated
types](https://github.com/coder/coder/blob/33d62619225702257fa2542f40ecc26bfd0d1fa6/site/src/api/typesGenerated.ts#L727),
which the frontend assumes are correct, and doesn't run additional
checks on.

- `features: Record<FeatureName, Feature>`: this type signifies that
every `FeatureName` is present in the record, but on `main`, that's not
true if there's a telemetry required error
- `warnings: readonly string[];` and `errors: readonly string[];`: these
types mean that the fields are not `null`, but that's not always true

With a valid license, the [`LicensesEntitlements`
function](https://github.com/coder/coder/blob/33d62619225702257fa2542f40ecc26bfd0d1fa6/enterprise/coderd/license/license.go#L92)
ensures that all features are present in the entitlements. It's called
by the [`Entitlements`
function](https://github.com/coder/coder/blob/33d62619225702257fa2542f40ecc26bfd0d1fa6/enterprise/coderd/license/license.go#L42),
which is called by
[`api.updateEnittlements`](https://github.com/coder/coder/blob/33d62619225702257fa2542f40ecc26bfd0d1fa6/enterprise/coderd/coderd.go#L687).
However, when a license requires telemetry and telemetry is disabled,
the entitlements with all features [are
discarded](https://github.com/coder/coder/blob/33d62619225702257fa2542f40ecc26bfd0d1fa6/enterprise/coderd/coderd.go#L704)
in an early exit from the same function. By initializing entitlements
with all the features from the get go, we avoid this problem.

## License issue banner after the changes

<img width="1512" alt="Screenshot 2025-02-23 at 20 25 42"
src="https://github.com/user-attachments/assets/ee0134b3-f745-45d9-8333-bfa1661e33d2"
/>

coderd/entitlements/entitlements.go

@@ -30,8 +30,8 @@ func New() *Set {
 		// These will be updated when coderd is initialized.
 		entitlements: codersdk.Entitlements{
 			Features:         map[codersdk.FeatureName]codersdk.Feature{},
-			Warnings:         nil,
-			Errors:           nil,
+			Warnings:         []string{},
+			Errors:           []string{},
 			HasLicense:       false,
 			Trial:            false,
 			RequireTelemetry: false,
@@ -39,13 +39,21 @@ func New() *Set {
 		},
 		right2Update: make(chan struct{}, 1),
 	}
+	// Ensure all features are present in the entitlements. Our frontend
+	// expects this.
+	for _, featureName := range codersdk.FeatureNames {
+		s.entitlements.AddFeature(featureName, codersdk.Feature{
+			Entitlement: codersdk.EntitlementNotEntitled,
+			Enabled:     false,
+		})
+	}
 	s.right2Update <- struct{}{} // one token, serialized updates
 	return s
 }
 
 // ErrLicenseRequiresTelemetry is an error returned by a fetch passed to Update to indicate that the
 // fetched license cannot be used because it requires telemetry.
-var ErrLicenseRequiresTelemetry = xerrors.New("License requires telemetry but telemetry is disabled")
+var ErrLicenseRequiresTelemetry = xerrors.New(codersdk.LicenseTelemetryRequiredErrorText)
 
 func (l *Set) Update(ctx context.Context, fetch func(context.Context) (codersdk.Entitlements, error)) error {
 	select {