py/grammar: Group no-compile grammar rules together to shrink tables.
Grammar rules have 2 variants: ones that are attached to a specific compile function which is called to compile that grammar node, and ones that don't have a compile function and are instead just inspected to see what form they take. In the compiler there is a table of all grammar rules, with each entry having a pointer to the associated compile function. Those rules with no compile function have a null pointer. There are 120 such rules, so that's 120 words of essentially wasted code space. By grouping together the compile vs no-compile rules we can put all the no-compile rules at the end of the list of rules, and then we don't need to store the null pointers. We just have a truncated table and it's guaranteed that when indexing this table we only index the first half, the half with populated pointers. This patch implements such a grouping by having a specific macro for the compile vs no-compile grammar rules (DEF_RULE vs DEF_RULE_NC). It saves around 460 bytes of code on 32-bit archs.