Fix display of partitioned tables

[jonels-msft]

Fixes microsoft/azuredatastudio-postgresql#126
Fixes microsoft/azuredatastudio-postgresql#156

Before

After

[jonels-msft]

Tested on Postgres versions:

• 11.19
• 12.14
• 13.10
• 14.7
• 15.2

Using ADS running on Intel macOS.

Sample schema for partitioned table:

-- Example from https://www.postgresql.org/docs/current/ddl-partitioning.html

CREATE TABLE measurement (
    city_id         int not null,
    logdate         date not null,
    peaktemp        int,
    unitsales       int
) PARTITION BY RANGE (logdate);

CREATE TABLE measurement_y2006m02 PARTITION OF measurement
    FOR VALUES FROM ('2006-02-01') TO ('2006-03-01');

CREATE TABLE measurement_y2006m03 PARTITION OF measurement
    FOR VALUES FROM ('2006-03-01') TO ('2006-04-01');