Add set_limit() fn to std::io::Take

[carllerche]

std::io::Cursor has a fn to update the position yet Take does not have a fn for setting the limit. Being able to update the limit is required for implementing various traits for Take. For example, Read works by updating the limit.

I was hoping to implement Buf for Take (in the bytes crate) but am currently unable to do so.

[carllerche]

It would also be nice if Take implemented:

• get_ref
• get_mut
• into_inner

[Mark-Simulacrum]

This is only missing the set_limit function today, as the rest are implemented (tracked, in part, by #41519). I've filed #42697 to implement set_limit.