Fix rename+overwrite GDrive case

[PVince81]

Description

Prevents having duplicate files appear in GDrive by properly explicitly
deleting the target file. This is because GDrive allows having multiple files with the same file name inside the same folder...

Related Issue

Fixes #25827

Motivation and Context

How Has This Been Tested?

• TEST: manual test with Webdav overwrite (cadaver)
• TEST: unit test

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

More tests fail now than before:

There were 4 failures:

1) OCA\Files_External\Tests\Storage\GoogleTest::testStat
Failed asserting that false is true.

/srv/www/htdocs/owncloud/tests/lib/Files/Storage/Storage.php:288

2) OCA\Files_External\Tests\Storage\GoogleTest::testRenameOverWriteDirectory
target/test2.txt has not been removed
Failed asserting that true is false.

/srv/www/htdocs/owncloud/tests/lib/Files/Storage/Storage.php:491

3) OCA\Files_External\Tests\Storage\GoogleTest::testRenameOverWriteDirectoryOverFile
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'foo'
+'bar'

/srv/www/htdocs/owncloud/tests/lib/Files/Storage/Storage.php:505

4) OCA\Files_External\Tests\Storage\GoogleTest::testCopyOverWriteDirectory
Failed asserting that true is false.

/srv/www/htdocs/owncloud/tests/lib/Files/Storage/Storage.php:543

FAILURES!
Tests: 81, Assertions: 422, Failures: 4

Known previous failures: #22481

[mention-bot]

@PVince81, thanks for your PR! By analyzing the annotation information on this pull request, we identified @AdamWill, @icewind1991, @MTGap and @Xenopathic to be potential reviewers

[PVince81]

I'll have another look at this for 10.0.1

[PVince81]

did not work. to be reconsidered in https://github.com/owncloud/files_external_gdrive