Auto merge of #51033 - coryshrmn:master, r=dtolnay

Auto merge of #51033 - coryshrmn:master, r=dtolnay

stabilize RangeBounds collections_range #30877

The FCP for #30877 closed last month, with the decision to:
1. move from `collections::range::RangeArgument` to `ops::RangeBounds`, and
2. rename `start()` and `end()` to `start_bounds()` and `end_bounds()`.

Simon Sapin already moved it to `ops::RangeBounds` in #49163.

I renamed the functions, and removed the old `collections::range::RangeArgument` alias.

This is my first Rust PR, please let me know if I can improve anything. This passes all tests for me, except the `clippy` tool (which uses `RangeArgument::start()`).

I considered deprecating `start()` and `end()` instead of removing them, but the contribution guidelines indicate we can break `clippy` temporarily. I thought it was best to remove the functions, since we're worried about name collisions with `Range::start` and `end`.

Closes #30877.