[metadata] Don't access MonoTableInfo:rows, use table_info_get_rows() (#49738)

[metadata] Don't access MonoTableInfo:rows, use table_info_get_rows() (#49738)

Rename the field to `rows_`.

Also updated some bounds checks to use `mono_metadata_table_bounds_check` (which is metadata-update aware) where the subsequent lookups go through the metadata decode functions and should just work with metadata-update.

Added `FIXME: metadata-update` in cases where the table row size is assumed to be
fixed or is used as a sentinel value, or where the decoding may depend on
sorting properties that metadata updates probably won't uphold.