perf(create-turbo): Download files faster (#11297)
### Description
I was becoming a little annoyed that `create-turbo` takes _so long_ to
download files. Even while I'm on a strong internet connection, it would
take something like 10 seconds.
Additionally, situations like
https://github.com/vercel/turborepo/issues/10456 were coming up because
getting the example onto the machine is so slow. It appears to be
hanging when its really just unexpectedly slow.
With some investigation, I found out that `create-turbo` was
downloading, **the entirety of `vercel/turborepo`** just to get the code
for an example. It turns out that this is a deficiency in GitHub's API;
you can't download subdirectories from a repo.
Instead, we can do sparse checkouts without the lightest-weight git
options that we can to improve performance as much as possible.
### Testing Instructions
I'm hand-testing the binary and it's significantly faster.
```
▲ 👟 ~/projects/debugs
hyperfine \
-r 5 \
--prepare 'rm -rf ./benchies' \
--cleanup 'rm -rf ./benchies' \
-n 'Old' 'npx create-turbo ./benchies --skip-install --skip-transforms' \
-n 'New' 'node ~/projects/open/turbo/packages/create-turbo/dist/cli.js ./benchies --skip-install --skip-transforms'
Benchmark 1: Old
Time (mean ± σ): 37.377 s ± 3.938 s [User: 2.602 s, System: 1.044 s]
Range (min … max): 31.170 s … 41.525 s 5 runs
Benchmark 2: New
Time (mean ± σ): 2.985 s ± 0.098 s [User: 0.659 s, System: 0.323 s]
Range (min … max): 2.890 s … 3.107 s 5 runs
Summary
New ran
12.52 ± 1.38 times faster than Old
```
<sub>Closes https://github.com/vercel/turborepo/issues/10456</sub>
<sub> Closes TURBO-5050</sub>
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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
