Rename to uv (#1302)

First, replace all usages in files in-place. I used my editor for this.
If someone wants to add a one-liner that'd be fun.

Then, update directory and file names:

```
# Run twice for nested directories
find . -type d -print0 | xargs -0 rename s/puffin/uv/g
find . -type d -print0 | xargs -0 rename s/puffin/uv/g

# Update files
find . -type f -print0 | xargs -0 rename s/puffin/uv/g
```

Then add all the files again

```
# Add all the files again
git add crates
git add python/uv

# This one needs a force-add
git add -f crates/uv-trampoline
```

scripts/benchmarks/uninstall.sh

@@ -13,5 +13,5 @@ set -euxo pipefail
 TARGET=${1}
 
 hyperfine --runs 20 --warmup 3 --prepare "rm -rf .venv && virtualenv .venv && source activate .venv/bin/activate && pip install ${TARGET}" \
-    "./target/release/puffin uninstall ${TARGET}" \
+    "./target/release/uv uninstall ${TARGET}" \
     "pip uninstall -y ${TARGET}"