If uv installed from uv tool install uv, allow call uv self update to update uv from pypi

[zhcn000000]

Summary

If uv installed from uv tool install uv,allow call uv self update to update uv from pypi
like

uv tool install uv

Because it is clearly an installation managed by uv.
I did this because using pip to install and upgrade uv is much faster than installing directly from the GitHub release version through script.

Example

so that we can use uv self update just like uv tool update uv when instelled from this chanel