Replace all db calls to aggregator_feed and aggregator_item tables with Entity APIs

Just a very first patch with one possible conversion, to see how it looks.

It's for AggregatorCronTest.

Looking at the remaining code, I now see

    $connection = Database::getConnection();
    $connection->update('aggregator_feed')
      ->condition('fid', $feed->id())
      ->fields([
        'queued' => REQUEST_TIME,
      ])
      ->execute();
    ...
    $connection->update('aggregator_feed')
      ->condition('fid', $feed->id())
      ->fields([
        'queued' => 0,
      ])
      ->execute();

and wonder if this is correct? Shouldn't this be managed via entity instead?

Addressed all the 'count' queries from #2994904-39: Convert query('SELECT ... FROM {xxx}') to select('xxx')->... in tests,

core/modules/aggregator/tests/src/Functional/AggregatorCronTest.php
core/modules/aggregator/tests/src/Functional/DeleteFeedTest.php
core/modules/aggregator/tests/src/Functional/ImportOpmlTest.php
core/modules/taxonomy/tests/src/Functional/TermIndexTest.php

There are way more to do...

Trying going a bit more the Entity API way instead of the db way in the aggregator tests.

taxonomy_index table is defined through the entity schema, but it's not an entity itself so reverting to use db calls.

Still experimenting here.

Try this.

Re. #4:

it makes sense to rework tests to use entity api

then I think we need a meta and children since reworking tests like that is much bigger than just converting db calls.

Potential tests affected:
core\modules\aggregator\tests\src\Functional\FeedParserTest.php
core\modules\aggregator\tests\src\Functional\UpdateFeedItemTest.php
core\modules\block_content\tests\src\Functional\BlockContentSaveTest.php
core\modules\block_content\tests\src\Functional\BlockContentTranslationUITest.php
core\modules\content_moderation\tests\src\Functional\DefaultContentModerationStateRevisionUpdateTest.php
core\modules\file\tests\src\Functional\SaveUploadFormTest.php
core\modules\file\tests\src\Functional\SaveUploadTest.php
core\modules\file\tests\src\FunctionalJavascript\FileManagedFileElementTest.php
core\modules\node\tests\src\Functional\NodeAccessBaseTableTest.php
core\modules\node\tests\src\Functional\NodeAccessRecordsTest.php
core\modules\node\tests\src\Functional\NodeRevisionPermissionsTest.php
core\modules\node\tests\src\Functional\NodeRevisionsAllTest.php
core\modules\node\tests\src\Functional\NodeRevisionsTest.php
core\modules\node\tests\src\Functional\NodeTranslationUITest.php
core\modules\path\tests\src\Functional\PathTaxonomyTermTest.php
core\modules\taxonomy\tests\src\Functional\TermTranslationUITest.php
core\modules\user\tests\src\Kernel\UserInstallTest.php

I’ll finish converting the aggregator module.

This is meant to convert all of direct db access (query/delete/update) to aggregator_feed and aggregator_item tables, to Entity API and Entity Query API.

Reverted the changes for TermIndexTest that no longer belong here.

I'd rather change this issue title to point to conversion of the two entities, and create a new meta of which this one should be a child.

Updated issue title and summary.

Addressing failures.

One more. If this turns out green, it'd be ready for review.

Looks good.

Can someone open a followup to remove queries against the node table in:

• \Drupal\aggregator\Tests\AggregatorTestBase::getDefaultFeedItemCount
• \Drupal\Tests\aggregator\Functional\AggregatorTestBase::getDefaultFeedItemCount

Committed 1da1c2b and pushed to 8.7.x. Thanks!

Backported to 8.6.x too as this is test only change. Committed b7ef221 and pushed to 8.6.x. Thanks!