fix: vec! macro resolution via alloc::vec self-import

`use alloc::vec::{self, Vec};` relies on the `self` import also
bringing the `vec!` macro into scope alongside the `vec` module.
On some rustc versions this only resolves the module (type
namespace), so unqualified `vec![...]` calls in this file fail
with "cannot find macro `vec` in this scope".

Import `Drain` by name instead of the `vec` module, and fully
qualify the two `vec!` invocations (`alloc::vec!` / `$crate::alloc::vec!`)
so macro resolution no longer depends on the `self`-import quirk.

Signed-off-by: Ravi Chamarthy <ravi@ciroos.ai>

Author: ravi-ciroos

src/tinyvec.rs

@@ -1,6 +1,6 @@
 use super::*;
 
-use alloc::vec::{self, Vec};
+use alloc::vec::{Drain, Vec};
 use core::convert::TryFrom;
 use tinyvec_macros::impl_mirrored;
 
@@ -46,7 +46,7 @@ macro_rules! tiny_vec {
           f($crate::array_vec!($array_type => $($elem),*))
         }
         $crate::TinyVecConstructor::Heap(f) => {
-          f(vec![$($elem),*])
+          f($crate::alloc::vec![$($elem),*])
         }
       }
     }
@@ -707,7 +707,7 @@ impl<A: Array> TinyVec<A> {
     if len <= A::CAPACITY {
       TinyVec::Inline(ArrayVec::from_array_len(A::default(), len))
     } else {
-      TinyVec::Heap(vec![A::Item::default(); len])
+      TinyVec::Heap(alloc::vec![A::Item::default(); len])
     }
   }
 
@@ -1308,7 +1308,7 @@ pub enum TinyVecDrain<'p, A: Array> {
   #[allow(missing_docs)]
   Inline(ArrayVecDrain<'p, A::Item>),
   #[allow(missing_docs)]
-  Heap(vec::Drain<'p, A::Item>),
+  Heap(Drain<'p, A::Item>),
 }
 
 impl<'p, A: Array> Iterator for TinyVecDrain<'p, A> {