Remove deprecated strings offsets_begin

[davidwendt]

Description

Removes the deprecated cudf::strings_column_view::offsets_begin() and cudf::strings_column_view::offsets_end() member functions. These are replaced with offsetalator wrapper calls instead.

Checklist

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

[davidwendt]

Even though this is removing a deprecated function, changing this to breaking since consumers would be affected.

[davidwendt]

/merge

[vyasr]

Even though this is removing a deprecated function, changing this to breaking since consumers would be affected.

IMO every PR removing deprecated functions should be marked as breaking since that's when the functionality actually becomes unavailable. Conversely PRs that deprecate functionality typically shouldn't be marked as breaking since calling code will continue to work. Of course, it's a blurry line since code compiled with e.g. -Wno-error=deprecated-declarations will fail even on the deprecation.