Expand webUISharingExternal acceptance tests

[phil-davis]

Current webUISharingExternal acceptance tests check just basic cases of upload, overwrite, rename, delete in the top folder of the received share.

• do some file operations in sub-folders of the received share
• look through the apiFederation acceptance test scope in issue Expand apiFederation acceptance tests #34149 and design a moderate set of test scenarios for the webUI to at least cover "the basics" of those scenarios.

Keep in mind that webUI tests are slow! But the current webUI uses various "private" APIs that could behave differently to the public APIs used by the apiFederation acceptance test suite. Because of this, it is good to cover a good mix of scenarios in the webUI.

[ownclouders]

GitMate.io thinks possibly related issues are #33690 (cleanup acceptance tests WebDav trait), #22492 (test), #22485 (test), #31579 (test), and #31516 (Acceptance test coding standard changes).

[paurakhsharma]

@phil-davis, Should we close this?