maxIntersections: add sorting by weight

[furmur]

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add sorting by weight to fix dependence on the order of intervals when end of the one interval matches with start of the another interval

wrong behavior example:

CREATE TABLE test1(start Integer, end Integer) engine = Memory;
CREATE TABLE test2(start Integer, end Integer) engine = Memory;
INSERT INTO test1(start,end) VALUES (1,3),(3,5);
INSERT INTO test2(start,end) VALUES (3,5),(1,3);

void :) SELECT maxIntersections(start,end) from test1;

SELECT maxIntersections(start, end)
FROM test 

┌─maxIntersections(start, end)─┐
│                            1 │
└──────────────────────────────┘

1 rows in set. Elapsed: 0.002 sec. 

void :) SELECT maxIntersections(start,end) from test2;

SELECT maxIntersections(start, end)
FROM test2 

┌─maxIntersections(start, end)─┐
│                            2 │
└──────────────────────────────┘

1 rows in set. Elapsed: 0.003 sec.

expected to receive the same value 1 for both cases

patch fixes function by placing points with weight -1 before points with weight 1 and the same position

[alexey-milovidov]

Missing test.

[furmur]

thank you ) i had to check default sort behavior first