Cleanup tasks in the Settings code (#12125)

* inline call to `SettingsStore.isEnabled`

* Remove confusing `SettingsStore.isEnabled`

This was basically the same as `SettingsStore.canSetValue` only more confusing,
so let's get rid of it.

* Add `configDisablesSetting` value for Settings

The current magic where this only works for features (but not beta features!)
is, well, magical. And I need more flexibility here.

* Remove redundant levels constant `LEVELS_FEATURE`

I don't know if this was ever intended to have different semantics to
`LEVELS_DEVICE_ONLY_SETTINGS_WITH_CONFIG`, but if it was, those semantics
shuold have been written down. They now seem to be used entirely
interchangably.

src/components/views/elements/SettingsFlag.tsx

@@ -40,8 +40,6 @@ interface IProps {
 
 interface IState {
     value: boolean;
-    /** true if `SettingsStore.isEnabled` returned false. */
-    disabled: boolean;
 }
 
 export default class SettingsFlag extends React.Component<IProps, IState> {
@@ -52,7 +50,6 @@ export default class SettingsFlag extends React.Component<IProps, IState> {
 
         this.state = {
             value: this.getSettingValue(),
-            disabled: this.isSettingDisabled(),
         };
     }
 
@@ -72,15 +69,9 @@ export default class SettingsFlag extends React.Component<IProps, IState> {
             this.props.isExplicit,
         );
     }
-
-    private isSettingDisabled(): boolean {
-        return !SettingsStore.isEnabled(this.props.name);
-    }
-
     private onSettingChange = (): void => {
         this.setState({
             value: this.getSettingValue(),
-            disabled: this.isSettingDisabled(),
         });
     };
 
@@ -104,14 +95,13 @@ export default class SettingsFlag extends React.Component<IProps, IState> {
     };
 
     public render(): React.ReactNode {
-        const canChange = SettingsStore.canSetValue(this.props.name, this.props.roomId ?? null, this.props.level);
+        const disabled = !SettingsStore.canSetValue(this.props.name, this.props.roomId ?? null, this.props.level);
 
-        if (!canChange && this.props.hideIfCannotSet) return null;
+        if (disabled && this.props.hideIfCannotSet) return null;
 
         const label = this.props.label ?? SettingsStore.getDisplayName(this.props.name, this.props.level);
         const description = SettingsStore.getDescription(this.props.name);
         const shouldWarn = SettingsStore.shouldHaveWarning(this.props.name);
-        const disabled = this.state.disabled || !canChange;
 
         if (this.props.useCheckbox) {
             return (

src/components/views/settings/CryptographyPanel.tsx

@@ -62,7 +62,7 @@ export default class CryptographyPanel extends React.Component<IProps, IState> {
         }
 
         let noSendUnverifiedSetting: JSX.Element | undefined;
-        if (SettingsStore.isEnabled("blacklistUnverifiedDevices")) {
+        if (SettingsStore.canSetValue("blacklistUnverifiedDevices", null, SettingLevel.DEVICE)) {
             noSendUnverifiedSetting = (
                 <SettingsFlag
                     name="blacklistUnverifiedDevices"

src/components/views/settings/E2eAdvancedPanel.tsx

@@ -38,5 +38,5 @@ const E2eAdvancedPanel: React.FC = () => {
 export default E2eAdvancedPanel;
 
 export function isE2eAdvancedPanelPossible(): boolean {
-    return SettingsStore.isEnabled(SETTING_MANUALLY_VERIFY_ALL_SESSIONS);
+    return SettingsStore.canSetValue(SETTING_MANUALLY_VERIFY_ALL_SESSIONS, null, SettingLevel.DEVICE);
 }

src/components/views/settings/tabs/room/SecurityRoomSettingsTab.tsx

@@ -427,7 +427,10 @@ export default class SecurityRoomSettingsTab extends React.Component<IProps, ISt
         const canEnableEncryption = !isEncrypted && !isEncryptionForceDisabled && hasEncryptionPermission;
 
         let encryptionSettings: JSX.Element | undefined;
-        if (isEncrypted && SettingsStore.isEnabled("blacklistUnverifiedDevices")) {
+        if (
+            isEncrypted &&
+            SettingsStore.canSetValue("blacklistUnverifiedDevices", this.props.room.roomId, SettingLevel.ROOM_DEVICE)
+        ) {
             encryptionSettings = (
                 <SettingsFlag
                     name="blacklistUnverifiedDevices"