Changes in default behavior:
1) INITIAL_HEAP is the new default for most builds.
   This means that there is an increase in the effective
   initial memory used by "sizeof(stack) + sizeof(static data)".
   In typical small applications this should be on the order
   of half a megabyte.
2) Because we cannot precisely calculate the amount
   of initial memory now, ASAN support will use
   the conservative upper estimate of MAXIMUM_MEMORY.
   This only affects ALLOW_MEMORY_GROWTH=0 builds.

This change does not yet enable INITIAL_HEAP for builds
that instantiate the memory in JS, e. g. with threading.

It seems this wasn't working for not-MINIMAL_RUNTIME
for similar reasons for some time already.

The tests hardcode the initial memory amount.
Make them robust against changes in defaults.

1 byte increase due to this diff:

-  (memory (;0;) 256 256)
+  (memory (;0;) 258 32768)

We no longer cap the maximum memory.

This is suspect...

Note that this will ignore user-supplied MAXIMUM_MEMORY when
growth is disabled. This is consistent with existing behavior.

Implementing ALLOW_MEMORY_GROWTH=0 properly revealed
an invalid assumption in the test: that MAXIMUM_MEMORY
is respected under ALLOW_MEMORY_GROWTH=0 (default).

Since this is not true, pass -sALLOW_MEMORY_GROWTH=1
alongside MAXIMUM_MEMORY.