fix: Remove unnecessary subquery for event data value [DHIS2-18417]

[larshelge]

This PR relates to event analytics table population. For pivoting event data element values to separate columns, a sub-query against the event table was used. This is unnecessary as the event table is the base table for the select statement, and the event data value can be retrieved directly using a JSON expression.

This change makes:

• The SQL query simpler.
• The insert into operation faster.
• The SQL query more standard and easier to map to other analytics database engines.

As an example, to retrieve a data value for a specific data element, instead of using a subquery against the event table, the SQL will check the value type (number, date, etc) and retrieve the value directly:

case
    when eventdatavalues #>> '{GieVkTxp4HH, value}' ~* '^(-?[0-9]+)(\.[0-9]+)?$' 
    then cast(eventdatavalues #>> '{GieVkTxp4HH, value}' as double precision)
    else null
end as "GieVkTxp4HH",

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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