Move `src/sidebar/{util/query-parser => helpers/query-parser}`

The loose distinction between `util/` and `helpers/` is that `util/` contains
more general-purpose code that might be useful outside of the client, whereas
`helpers/` contains more app-specific functions. The query parser is really the
latter as it is closely linked to the annotation filtering logic implemented in
`helpers/filter-annotations.ts`.

src/sidebar/components/StreamView.tsx

 import { useCallback, useEffect } from 'preact/hooks';
 
+import { parseHypothesisSearchQuery } from '../helpers/query-parser';
 import { withServices } from '../service-context';
 import type { APIService } from '../services/api';
 import type { ToastMessengerService } from '../services/toast-messenger';
 import { useSidebarStore } from '../store';
-import { parseHypothesisSearchQuery } from '../util/query-parser';
 import ThreadList from './ThreadList';
 import { useRootThread } from './hooks/use-root-thread';
 

src/sidebar/components/test/StreamView-test.js

@@ -40,7 +40,7 @@ describe('StreamView', () => {
     $imports.$mock({
       './hooks/use-root-thread': { useRootThread: fakeUseRootThread },
       '../store': { useSidebarStore: () => fakeStore },
-      '../util/query-parser': fakeQueryParser,
+      '../helpers/query-parser': fakeQueryParser,
     });
   });
 

src/sidebar/helpers/filter-annotations.ts

 import { cfiInRange, stripCFIAssertions } from '../../shared/cfi';
 import type { Annotation } from '../../types/api';
 import { pageLabelInRange } from '../util/page-range';
-import type { Facet } from '../util/query-parser';
 import * as unicodeUtils from '../util/unicode';
 import { cfi as getCFI, quote, pageLabel } from './annotation-metadata';
+import type { Facet } from './query-parser';
 
 type Filter = {
   matches: (ann: Annotation) => boolean;

src/sidebar/util/test/query-parser-test.js → src/sidebar/helpers/test/query-parser-test.js

 import { parseHypothesisSearchQuery, parseFilterQuery } from '../query-parser';
 
-describe('sidebar/util/query-parser', () => {
+describe('sidebar/helpers/query-parser', () => {
   function isEmptyFilter(filter) {
     return Object.values(filter).every(value => value.length === 0);
   }

src/sidebar/helpers/test/thread-annotations-test.js

@@ -44,7 +44,7 @@ describe('sidebar/helpers/thread-annotations', () => {
 
     $imports.$mock({
       './build-thread': { buildThread: fakeBuildThread },
-      '../util/query-parser': fakeQueryParser,
+      './query-parser': fakeQueryParser,
       './filter-annotations': { filterAnnotations: fakeFilterAnnotations },
     });
   });

src/sidebar/helpers/thread-annotations.ts

 import type { Annotation } from '../../types/api';
 import { memoize } from '../util/memoize';
-import { parseFilterQuery } from '../util/query-parser';
 import { buildThread } from './build-thread';
 import type { Thread, BuildThreadOptions } from './build-thread';
 import { filterAnnotations } from './filter-annotations';
+import { parseFilterQuery } from './query-parser';
 import { shouldShowInTab } from './tabs';
 import { sorters } from './thread-sorters';