Remove all uses of the obsolete wrappers init_alloc() and sql_alloc().

This is done 99% mechanically, with Perl and clang-format; there was
one case in opt_range.cc that required manual intervention (a ternary
expression used for the MEM_ROOT), and of course the removals themselves.

Change-Id: Iaa11deadbded0253a6b5e0dd3a417c650a4692fa