Single install command

[krisl]

No description provided.

[Copilot]

Pull Request Overview

This PR introduces a "single install command" feature that allows package installers to use a single invocation to install multiple packages instead of running separate commands for each package. The change is controlled by a new --one-shot command line option that accepts installer names like "apt" or "pip".

Key changes:

• Adds --one-shot command line option to enable single-command installation for specified installers
• Modifies installer interfaces to support the oneshot parameter
• Updates both apt and pip installers to combine multiple packages into single install commands when oneshot is enabled

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/rosdep2/main.py	Adds --one-shot command line option and passes it through to installation logic
src/rosdep2/installers.py	Updates installer base classes and installation flow to support oneshot parameter
src/rosdep2/platforms/debian.py	Implements oneshot support for apt installer, combining packages into single command
src/rosdep2/platforms/pip.py	Implements oneshot support for pip installer, combining packages into single command
test/test_rosdep_main.py	Adds test case for --one-shot functionality with apt installer
test/test_rosdep_pip.py	Adds test cases for oneshot functionality in pip installer
test/test_rosdep_debian.py	Adds test cases for oneshot functionality in debian/apt installer and removes debug print
test/test_rosdep_installers.py	Updates test expectations to match new single-command output format

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