BookmarkRepository::getList() only matched bookmarks scoped to the exact
requested database, so bookmarks created without a database context
(dbase = '', e.g. via the Console, which does not require a database to
be selected) never showed up when browsing a specific database's
bookmark list. The dbase filter now also matches an empty dbase.

BookmarkRepository::getByLabel() ignored AllowSharedBookmarks entirely,
requiring an exact user match. This method backs
Sql::getDefaultSqlQueryForBrowse() (the per-table default browse query
feature documented in FAQ 6.22), so a bookmark shared by another user
never applied for anyone else, unlike get()/getList() which already
honored the setting. getByLabel() now falls back to an empty user the
same way the other two do.

Extracted the repeated "exact user match, falling back to shared" SQL
fragment into a single userMatchCondition() helper used by get(),
getList() and getByLabel(). Without it, fixing getByLabel() would have
copied a third instance of the same conditional that get()/getList()
already duplicated between them.

Updated docblocks on all three methods to state the actual contract
(shared-across-user and shared-across-database fallback behavior)
instead of paraphrasing the method names; getByLabel() now references
its real caller so the "why" of the shared-label lookup is not left
implicit.

Added 8 new tests covering both fixes and their AllowSharedBookmarks-off
counterparts, plus the previously untested positive-match path for
get(). Updated the two existing tests (BookmarkTest::testGetList and the
DbiDummy fixture used by ReplaceControllerTest::testReplace) that had
the old SQL text hardcoded, since DbiDummy matches queries by exact
string.

Signed-off-by: Willian Cavalcante <248522986+cavalcante-willian@users.noreply.github.com>