Rollup merge of rust-lang#140983 - tkr-sh:master, r=ibraheemdev

Improve doc of some methods that take ranges

Some methods that were taking some range in parameter were a bit inconsistent / unclear in the panic documentation.

Here is the recap:
- Replaced "start/end point" by "start/end bound" to be coherent with [`RangeBounds`](https://doc.rust-lang.org/stable/std/ops/trait.RangeBounds.html) naming (it's also easier to understand I think)
- Previously, it was written "_[...] or if the end point is greater than the length of [...]_", but this is not entirely true! Actually, you can have a start bound that is greater than the length, with an end bound that is unbounded and it will also panic. Therefore I think that "_[...] one of the range bound is bounded and greater than the length of [...]_" is better!
- `String` methods weren't mentionning that the method panics if `start_bound > end_bound` but it actually does! It uses `slice::range` which panics when `start > end`.  (https://doc.rust-lang.org/stable/src/alloc/string.rs.html#1932-1934, https://doc.rust-lang.org/stable/src/core/slice/index.rs.html#835-837).
You can also test it with:
```rs
struct MyRange;
impl std::ops::RangeBounds<usize> for MyRange {
    fn start_bound(&self) -> std::ops::Bound<&usize> {
        std::ops::Bound::Included(&3usize)
    }
    fn end_bound(&self) -> std::ops::Bound<&usize> {
        std::ops::Bound::Included(&1usize)
    }
}

fn main() {
    let mut s = String::from("I love Rust!");
    s.drain(MyRange); // panics!
}
```

Author: Zalathar

alloc/src/collections/vec_deque/mod.rs

@@ -1486,8 +1486,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point is greater than the end point or if
-    /// the end point is greater than the length of the deque.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and past the length of the deque.
     ///
     /// # Examples
     ///
@@ -1522,8 +1522,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point is greater than the end point or if
-    /// the end point is greater than the length of the deque.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and past the length of the deque.
     ///
     /// # Examples
     ///
@@ -1568,8 +1568,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point is greater than the end point or if
-    /// the end point is greater than the length of the deque.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and past the length of the deque.
     ///
     /// # Leaking
     ///

alloc/src/string.rs

@@ -1117,8 +1117,8 @@ impl String {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point or end point do not lie on a [`char`]
-    /// boundary, or if they're out of bounds.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and does not lie on a [`char`] boundary.
     ///
     /// # Examples
     ///
@@ -1939,8 +1939,8 @@ impl String {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point or end point do not lie on a [`char`]
-    /// boundary, or if they're out of bounds.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and does not lie on a [`char`] boundary.
     ///
     /// # Leaking
     ///
@@ -2050,8 +2050,8 @@ impl String {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point or end point do not lie on a [`char`]
-    /// boundary, or if they're out of bounds.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and does not lie on a [`char`] boundary.
     ///
     /// # Examples
     ///

alloc/src/vec/mod.rs

@@ -2796,8 +2796,8 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point is greater than the end point or if
-    /// the end point is greater than the length of the vector.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and past the length of the vector.
     ///
     /// # Leaking
     ///
@@ -3860,8 +3860,8 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// # Panics
     ///
-    /// Panics if the starting point is greater than the end point or if
-    /// the end point is greater than the length of the vector.
+    /// Panics if the range has `start_bound > end_bound`, or, if the range is
+    /// bounded on either end and past the length of the vector.
     ///
     /// # Examples
     ///