Fix line/area graph (broken after recent changes)

[rdwebdesign]

What does this PR aim to accomplish?

Fix 3 small issues:

• A recent optimization (Simplify how data is passed to Long term graph #2374) broke the line graph in specific situations.
  Details: Simplify how data is passed to Long term graph #2374 (comment)

• Also, in some cases the 2 values (domains and blocked queries) were "out of sync", showing slightly different timestamps, possibly creating more bars than expected.

• Queries with status code equal 15 or 16 are not counted as blocked, but they should be, as noted by @yubiuser.

How does this PR accomplish the above?

• Re-add the function to fill the "gaps" with zeros;
• Simplify SQL using a single query to retrieve both values (domains and blocked queries) using the exact same timestamps.
• Add queries with codes 15 or 16 to the blocked count.

What documentation changes (if any) are needed to support this PR?

none

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[yubiuser]

Do we still need

    $stmt->bindValue(':from', $from, SQLITE3_INTEGER);
    $stmt->bindValue(':until', $until, SQLITE3_INTEGER);

[rdwebdesign]

Do we still need

    $stmt->bindValue(':from', $from, SQLITE3_INTEGER);
    $stmt->bindValue(':until', $until, SQLITE3_INTEGER);

Yes. :from and :until are used on the WHERE clause. They are in $limit variable.