Special-case reinstalls in environment update summaries

[zanieb]

e.g.

❯ uv pip install httpx==0.26.0 --reinstall-package httpx
Resolved 7 packages in 67ms
Prepared 1 package in 0.95ms
Uninstalled 1 package in 2ms
Installed 1 package in 12ms
 ~ httpx==0.26.0

❯ uv add httpx==0.26.0
warning: `uv add` is experimental and may change without warning
warning: `uv.sources` is experimental and may change without warning
Resolved 15 packages in 23ms
   Built example @ file:///Users/zb/workspace/example
Prepared 2 packages in 187ms
Uninstalled 2 packages in 2ms
Installed 2 packages in 2ms
 ~ example==0.1.0 (from file:///Users/zb/workspace/example)
 - httpx==0.27.0
 + httpx==0.26.0

Motivated by trying to reduce the diff for project updates in uv add. I think it makes sense in general though. We'll also want a special output for upgrades in the future, e.g. reducing the httpx changes in the second example to a single line indicating the original and subsequent distribution versions.

I'd like to have

Reinstalled 1 package in 2ms

but it seems non-trivial to show the timing for it? I think we'd need to determine what we want to call a "Reinstall" during the operations and split doing them from the rest of the uninstalls and installs.

[zanieb]

It looks like we could determine reinstalls and upgrades from the Plan. I've got some follow-up work-in-progress that shifts to doing that, but I don't think it blocks this change.

[charliermarsh]

This looks reasonable to me.