After returning from the callback in st_update is the point that the
hash table may be resized, which could trigger a GC and mark the table
being used for the tally.

    RUBY_GC_LIBRARY=wbcheck WBCHECK_VERIFY_AFTER_WB=1 ./miniruby -e '(0...100).map(&:to_s).tally'

	[Bug #21008] Normalize before sum to float

	After switching to `Float`-mode when summing `Numeric` objects,
	normalization for `Float` is still needed.

* Remove 1 allocation in Enumerable#each_with_index

Previously, each call to Enumerable#each_with_index allocates 2
objects, one for the counting index, the other an imemo_ifunc passed
to `self.each` as a block.

Use `struct vm_ifunc::data` to hold the counting index directly to
remove 1 allocation.

* [DOC] Brief summary for usages of `struct vm_ifunc`

This is a follow up to 182822683f86c8f8d63b05765addf5a04d112aa2.

Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>

Enumerable#all?, #any?, #one?, and #none? do not use yielded arguments
as an Array. So they can use rb_block_call2 to omit array allocatoin.

Enumerable#find does not have to immediately accept yielded arguments as
an Array. It can delay array allocation until the predicate block
returns truthy.

(TODO: Enumerable#count and #find_all seem to be optimizable as well.)

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
Co-authored-by: Dennis Dashkevich <dskecse@gmail.com>