Lower precision for a number of queries.

These queries are currently run by default, but don't have their results displayed.

Looking through results on LGTM.com, they are either false positives (e.g., `BitwiseSignCheck` which flags many perfectly harmless operations and `CompareIdenticalValues` which mostly flags NaN checks) or harmless results that developers are unlikely to care about (e.g., `EmptyArrayInit` or `MisspelledIdentifier`).

With this PR, the only queries that are still run but not displayed are security queries, where different considerations may apply.

javascript/ql/src/Statements/EphemeralLoop.ql

@@ -6,7 +6,7 @@
  * @problem.severity recommendation
  * @id js/single-run-loop
  * @tags readability
- * @precision high
+ * @precision low
  */
 
 import javascript

javascript/ql/src/Statements/NestedLoopsSameVariable.ql

@@ -7,7 +7,7 @@
  * @id js/nested-loops-with-same-variable
  * @tags maintainability
  *       correctness
- * @precision medium
+ * @precision low
  */
 
 import javascript

javascript/ql/src/Statements/ReturnOutsideFunction.ql

@@ -7,7 +7,7 @@
  * @id js/return-outside-function
  * @tags reliability
  *       correctness
- * @precision medium
+ * @precision low
  */
 
 import javascript