Decimal handling for sqlite (on windows) breaks intermittently

[neilotoole]

Describe the bug
It's well-known that SQLite is loosey-goosey with type handling. In particular, it doesn't really support decimal / numeric.

A recent PR introduced a dedicated decimal.Decimal type into the codebase. However, even using that type, SQLite exhibits intermittent undesired behavior on Windows: it sometimes returns a decimal value as a REAL/float, but not with the correct (round) value. E.g. see this pipeline.

    db_type_test.go:193: 
        	Error Trace:	D:/a/sq/sq/drivers/sqlite3/db_type_test.go:193
        	Error:      	Not equal: 
        	            	expected: decimal.Decimal{value:(*big.Int)(0xc000402de0), exp:-2}
        	            	actual  : decimal.Decimal{value:(*big.Int)(0xc000402400), exp:-14}
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -4,6 +4,6 @@
        	            	   abs: (big.nat) (len=1) {
        	            	-   (big.Word) 7777
        	            	+   (big.Word) 7777000000000001
        	            	   }
        	            	  }),
        	            	- exp: (int32) -2
        	            	+ exp: (int32) -14
        	            	 }
        	Test:       	TestDatabaseTypes
        	Messages:   	type_test__b5wvrewy_0[1][17] (col_decimal) expected decimal.Decimal(77.77) but got decimal.Decimal(77.77000000000001)

To Reproduce

This happens intermittently on the GH windows runner. Usually re-running the job will result in the correct value. However, those intermittently failing tests are currently deliberately skipped. To reproduce, unskip the tests.

Expected behavior

The exact decimal/numeric value should be returned every time.

sq version

This happens on master pipeline, intermittently.