Search query is especially slow if a user searches a generic string
which matches many records, in such case search can take tens of
seconds or time out. To speed up the search query, we search only for
first 1000 records, if there is >1000 matching records we just display
"1000+" instead of precise total count supposing that with such amount
the exact count is not so important for the user.

Because for issues even limited search was not fast enough, 2-phase
approach is used for issues: first we use simpler/faster query to get
all public issues, if this exceeds the limit, we just return the limit.
If the amount of matching results is lower than limit, we re-run more
complex search query (which includes also confidential issues).
Re-running the complex query should be fast enough in such case because the
amount of matching issues is lower than limit.

Because exact total_count is now limited, this patch also switches to
to "prev/next" pagination.

Related #40540

rework indexes on redirect_routes

See merge request gitlab-org/gitlab-ce!16211

Signed-off-by: Rémy Coutable <remy@rymai.me>

[10.3] Migrate `can_push` column from `keys` to `deploy_keys_project`

See merge request gitlab/gitlabhq!2276

(cherry picked from commit f6ca52d31bac350a23938e0aebf717c767b4710c)

1f2bd3c0 Backport to 10.3

Previously, the last push widget would only show when the branch never had
a merge request associated with it - even merged or closed ones. Now the
widget will disregard merge requests that are merged or closed.