fix(core): fix non-partitioned table truncate error

[ideoma]

Fix the error when a non-partitioned table has a column deleted and then truncated.

java.lang.UnsupportedOperationException: null
	at io.questdb.cairo.vm.api.NullMemory.getFd(NullMemory.java:82)
	at io.questdb.cairo.vm.api.MemoryM.isOpen(MemoryM.java:57)
	at io.questdb.cairo.TableWriter.truncate(TableWriter.java:2165)
	at io.questdb.test.griffin.wal.fuzz.TruncateTableOperation.apply(TruncateTableOperation.java:33)
	at io.questdb.test.griffin.O3MaxLagTest.replayTransactions(O3MaxLagTest.java:436)
	at io.questdb.test.griffin.O3MaxLagTest.testFuzz00(O3MaxLagTest.java:514)
	at io.questdb.test.griffin.O3MaxLagTest.testFuzz0(O3MaxLagTest.java:807)

Also, move fuzz (random number generated) test cases into classes with Fuzz in their name to be picked up for Fuzz test CI runs.

[ideoma]

[PR Coverage check]

😍 pass : 10 / 10 (100.00%)

file detail

	path	covered line	new line	coverage
🔵	io/questdb/cairo/TableWriter.java	10	10	100.00%