[ticket/8610] Merging topics does not handle bookmarks correctly

https://tracker.phpbb.com/browse/PHPBB3-8610

PHPBB3-8610
[ticket/8610] Fix bookmarks when merging all the posts of a topic

PHPBB3-8610
[ticket/8610] Throw an error when the dest topic isn't set

PHPBB3-8610
[ticket/8610] Add functional test when two topics are merged

PHPBB3-8610
[ticket/8610] Use css selector instead of xPath

PHPBB3-8610
[ticket/12606] Add ACP group core events

PHPBB3-12606
[ticket/12667] Do not point viewtopic URL to unread post outside of view=unread

PHPBB3-12667
Merge pull request #2434 from Nicofuma/ticket/8610

[ticket/8610] Merging topics does not handle bookmarks correctly

* Nicofuma/ticket/8610:
  [ticket/8610] Use css selector instead of xPath
  [ticket/8610] Add functional test when two topics are merged
  [ticket/8610] Throw an error when the dest topic isn't set
  [ticket/8610] Fix bookmarks when merging all the posts of a topic
  [ticket/8610] Merging topics does not handle bookmarks correctly
Merge pull request #2568 from prototech/ticket/12667

[ticket/12667] Do not point viewtopic URL to unread post outside of view=unread.

* prototech/ticket/12667:
  [ticket/12667] Do not point viewtopic URL to unread post outside of view=unread
Merge pull request #2518 from Pico88/ticket/12606

[ticket/12606] Add ACP group core events

* Pico88/ticket/12606:
  [ticket/12606] Add ACP group core events
[ticket/12664] Refactor develop/migration_tips.php into a console command.

PHPBB3-12664
Merge pull request #2569 from bantu/ticket/12664

[ticket/12664] Refactor develop/migration_tips.php into a console command.

* bantu/ticket/12664:
  [ticket/12664] Refactor develop/migration_tips.php into a console command.
[ticket/12508] Remove extension manager from finder

PHPBB3-12508
[ticket/12508] Fix usages of the finder

PHPBB3-12508
[ticket/12508] Move \phpbb\extension\finder to \phpbb\finder

PHPBB3-12508
[ticket/12508] Fix class doc block

PHPBB3-12508
[ticket/12508] Only take a list of names for set_extensions()

PHPBB3-12508
[ticket/12508] Add a unit test for set_extensions()

PHPBB3-12508
[ticket/12508] Add new line to separate the if and foreach better

PHPBB3-12508
[ticket/12508] Fix doc block

PHPBB3-12508