vinyl: fix page_size and range_size defaults

If the value of range_size is absent in the _index system space, it will
be initialized to 0 in struct index_def. This will lead to insane range
splitting in vinyl and, as a result, file descriptor exhaustion. We ran
into this problem after restoring memtx spaces as vinyl using tarantool
dump utility (the latter simply replaces 'memtx' with 'vinyl' in the
_space system space on restore). To avoid a debacle like this in future,
let's use hardcoded defaults if vinyl options were omitted in the _index
system space on insertion. The default values are the same we use for
the corresponding box.cfg options. We already do it for run_size_ratio,
run_count_per_level, and bloom_fpr so let's do it for range_size and
page_size too.

Closes #3019