Decide on a naming convention for casting methods.

[Kimundi]

There are often situations where you need similar-but-distinct names for functions that allow you to

• convert &self to &T for some T != Self
• convert self to T for some T != Self
• copy &self to T for some T != Self

Those functions at the moment are named in a very ad-hoc fashion: to_bytes(), slice_str(), as_char(), to_bytes_consume() etc. A standard naming convention would allow to see at a glance what the function does.

One possible set of names could be:

• to_TYPE() for a copy/new allocation.
• as_TYPE() for a reference/slice.
• into_TYPE() for consuming self and returning the target type without copy.

[thestinger]

There's still no consistent convention across the codebase.

[erickt]

Closing this in favor of #7087, which has a longer discussion.