Update typeof. Support of single quoted JSON

[tartas1]

This fix is adding support for single-quoted JSON.
Currently, it works only with double-quoted JSON. There is no way to check JSON containing strings, dictionaries and lists.

This works:
SELECT typeof(JSON "null");
SELECT typeof(JSON "100");

This won't work:
SELECT typeof(JSON '"text"');
SELECT typeof(JSON '{"gate": "A4", "flight_number": 2005}');

==========================================================================
Fixed EXAMPLE:
CREATE temp FUNCTION typeof (input ANY TYPE)
AS ( (
SELECT
CASE
-- Process NUMERIC, DATE, DATETIME, TIME, TIMESTAMP,
WHEN REGEXP_CONTAINS(literal, r'^[A-Z]+ ("|')') THEN REGEXP_EXTRACT(literal, r'^([A-Z]+) (?:"|')') --modified regexp
WHEN REGEXP_CONTAINS(literal, r'^-?[0-9]$') THEN 'INT64'
WHEN REGEXP_CONTAINS(literal, r'^(-?[0-9]+[.e].|CAST("([^"]*)" AS FLOAT64))$') THEN 'FLOAT64'
WHEN literal IN ('true', 'false') THEN 'BOOL'
WHEN literal LIKE '"%' OR literal LIKE "'%" THEN 'STRING'
WHEN literal LIKE 'b"%' THEN 'BYTES'
WHEN literal LIKE '[%' THEN 'ARRAY'
WHEN REGEXP_CONTAINS(literal, r'^(STRUCT)?(') THEN 'STRUCT'
WHEN literal LIKE 'ST_%' THEN 'GEOGRAPHY'
WHEN literal = 'NULL' THEN 'NULL'
ELSE
'UNKNOWN'
END
FROM
UNNEST([FORMAT('%T', input)]) AS literal));

SELECT typeof(JSON '"text"');
SELECT typeof(JSON '{"gate": "A4", "flight_number": 2005}');

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