Add recipe for gz-launch

[traversaro]

The ignition robotics libraries, that are currently packaged in conda-forge under the libignition-*, have been renamed to Gazebo libraries (see https://community.gazebosim.org/t/a-new-era-for-gazebo/1356).

To avoid confusion related to the feedstock name in the future, we are re-submitting all the libignition- recipes to conda-forge to have descriptive and coherent names that start with gz-, as described in conda-forge/libignition-cmake0-feedstock#26 (comment) .

This PR creates a new gz-launch-feedstock to package gz-launch, using the recipe already available in https://github.com/conda-forge/libignition-launch-feedstock .

As discussed in conda-forge/libignition-cmake0-feedstock#26, for consistency with Gazebo/Ignition libraries that have Python bindings also this PRs structured the recipe as a multiple-output one, in which the gz-launch6 package is used to install all the outputs.

Checklist

• Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml".
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• Source is from official source.
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• Build number is 0.
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• GitHub users listed in the maintainer section have posted a comment confirming they are willing to be listed there.
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[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/gz-launch) and found it was in an excellent condition.

[traversaro]

Approval of being mantainers from the mantainers (i.e. GitHub users listed in the maintainer section have posted a comment confirming they are willing to be listed there.)

• @wolfv: Add recipe for gz-cmake #20547 (comment)
• @Tobias-Fischer: Add recipe for gz-utils #20593 (comment)

@conda-forge/help-c-cpp The recipe is ready for review.