… to tool (#4268)

Eliminates the remaining logic from tool_runner.sh, completing the goal of migrating repository tooling off of bash (both to make maintenance easier, and to better support Windows both locally and in CI). Its branch-based logic is now part of the tool itself, via a new `--packages-for-branch` flag (which is hidden in help since it's only useful for CI).

Part of flutter/flutter#86113

Moves `publish` to PackageLoopingCommand, giving it the same
standardized output and summary that is used by most other commands in
the tool.

Adds minor new functionality to the base command to allow it to handle
the specific needs of publish:
- Allows fully customizing the set of packages to loop over, to support
  --all-changed
- Allows customization of a few more strings so the output better
  matches the functionality (e.g., using 'published' instead of 'ran' in
  the summary lines).

Fixes flutter/flutter#83413

The build-examples command was filtering what it attempted to build by plugin platform, which means it never does anything for non-plugin packages. flutter/packages has steps that run this command, which suggests it used to work and regressed at some point, but nobody noticed; this will re-enable those builds so that we are getting CI coverage that the examples in flutter/packages build.

Mostly fixes flutter/flutter#88435 (needs a flutter/packages tool pin roll to pick this up)

- Adds a minimal unit test to url_launcher_linux as a proof of concept. This uses almost exactly the same CMake structure as the Windows version that was added recently.
- Adds Linux support for unit tests to `native-test`, sharing almost all of the existing Windows codepath.
- Fixes the fact that it it was running the debug version of the unit tests, but `build-examples` only builds release. (On other platforms we run debug unit tests, but on those platforms the test command internally builds the requested unit tests, so the mismatch doesn't matter.)
- Enables the new test in CI.

Also opportunistically fixes some documentation in `native_test_command.dart` that wasn't updated as more platform support was added.

Linux portion of flutter/flutter#82445

…tialized. (#4300)

See flutter/flutter#89373 for context. This
sets up the script and config file to replicate the current plugins.py
recipe's behavior using the planned generic recipe.

These are currently unused, but are being landed first so that the
generic recipe has something to test against.

Part of flutter/flutter#89373

Reverts #4288 which published a breaking change as if it were a non-breaking change.

The discussion in that PR prior to it landing was incorrect, because adding a new parameter
with a default value is non-breaking *only for clients*. It is breaking for subclasses that
override it, and the purpose of the platform interface is for implementations to subclass it
and override everything.

It's possible for jobs to conclude in a "neutral" state; see https://github.com/flutter/plugins/runs/3534917860 for instance. Currently this causes "release" to be red when it shouldn't be.