Add toKeysArray() and toValuesArray() to all collection types

Map and StableMap already have these APIs, let's add them to Vector, Set,
and Pair for consistency.

Reviewed By: @elgenie

Differential Revision: D979552
Fix traits bug with instance props that use collection literal initializers

This fixes a traits bug involving instance props that use collection literal
initializers. Instances of a class are not supposed to share the collection;
they are supposed to each get their own copy.

Reviewed By: @andralex

Differential Revision: D979933
Fix emalloc and spprintf

emalloc(n, size, offset) was ignoring the size and offset params,
and underallocating.

spprintf() wasn't allocating & copying the null terminator byte.

Reviewed By: @jdelong

Differential Revision: D979798
requestInit shouldn't clear Arrays again

On requestInit, if Arrays are null inited and reset during
shutdown, they shouldn't need to be reset again (it will just end up
doing redundant work) so just assert the expectation is the case.

Reviewed By: @markw65

Differential Revision: D978681
Fix array_cse/537.php

Its producing different warnings in different situations,
so just turn them off.

Reviewed By: @hermanventer

Differential Revision: D980191