Do not remove uv itself on pip sync

[flyaroundme]

Summary

Added uv to the list of the preserved packages when building the installer plan. In that case uv is not going to be removed when, for example, using python -m uv pip sync requirements.txt when requirements.txt does not contain uv, but uv is installed in that venv.

Closes #1631

Test Plan

Got through the example attached to #1631 and did not see the uv deletion in the output

$ python -m uv pip sync requirements.txt
Installed 1 package in 20ms
 + ruff==0.2.2

[charliermarsh]

Nice, thank you!

[charliermarsh]

Welcome to the project.