pip compile: exclude --upgrade-package when option and value are passed as a single argument - #5033

)

I messed up the order of checks in #5033, due to which it failed to
exclude the case of `-P package`, as `arg.startswith("-P")` check came
first and skipped only the first argument.

That means that, in the following command:
```console
uv pip compile --output-file pip_compile_uv_header.txt unpinned_uv.in -P attrs==18.1.0
```

The generated header would exclude `-P`, but keep `attrs==18.1.0`.

```plaintext
# This file was autogenerated by uv via the following command:
#    uv pip compile --output-file pip_compile_uv_header.txt unpinned_uv.in attrs==18.1.0
```

But we want to check for an exact match first and then only check for
the case when option and value are together.

This also affected `--find-links` short option of style `-f <uri>`.


Hopefully, third times going to be a charm. 😳 


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## Summary

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I tested locally, and also changed one snapshot test to use `-P` for
variation. I don't think it's worth an extra test, but can do that for
sure.