Add data-size member to libcudf column_view classes

[davidwendt]

Description

Adds new data-size member to the cudf::column_view, cudf::mutable_column_view, and cudf::column_device_view classes. This is working towards solving #13733 where the character column data may exceed a size_type. The size of the device buffer usually known since the data is stored in a rmm::device_buffer in the cudf::column class. This makes the size a requirement for building any of the various column_views though most are created through utilities. The size will only initially be needed when manipulating strings per #13733.

The size_bytes() name was chosen for consistency with string_view and device_span.

Depends on #14030

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[jrhemstad]

This should be clearer. Is it the number of bytes of a single element? size() * sizeof(T)?

[davidwendt]

It would be size() * sizeof(T) but only where T is a fixed-width-type.
The intention here is to expose the actual device-buffer size() which may be larger than sizeof(size_type) in the solutions we are looking at ways to allow the total number of bytes in a strings column to exceed size_type.

[jrhemstad]

I think a fundamental invariant is that column.size() * size_of(column.type() == column.size_bytes(). However, given that column::size() returns int, then that invariant can be violated which seems bad.

Are we planning to make column::size() also return size_t?

[davidwendt]

We are not changing size() but rather only adding size_bytes().

I think the invariant argument may break down with compounds types. We are only trying to solve for strings columns at this point.