fix(sql): fix sample by over subquery with explicit timestamp

[bziobrowski]

Fixes #3085

Subqueries with explicit timestamp, e.g.

( SELECT * FROM (X) TIMESTAMP(ts) ) 

are normally used because X doesn't produce timestamp metadata . Passing the 'timestamp required flag' down
into inner queries is likely to fail if X looks like :

  SELECT * FROM Y
  UNION ALL
  SELECT * FROM Z 
  ORDER BY ts

[ideoma]

[PR Coverage check]

😍 pass : 15 / 15 (100.00%)

file detail

	path	covered line	new line	coverage
🔵	io/questdb/griffin/SqlParser.java	1	1	100.00%
🔵	io/questdb/griffin/model/QueryModel.java	5	5	100.00%
🔵	io/questdb/griffin/SqlCodeGenerator.java	6	6	100.00%
🔵	io/questdb/griffin/SqlOptimiser.java	3	3	100.00%