Fair naming

[dmytrotkk]

This pull request replaces the "Mirage" build type with a new "Fair" build type across the project, updating workflows, documentation, and CLI commands. It also increments the version number and updates a submodule reference. The key changes are grouped into the following themes:

Workflow Updates:

• Updated .github/workflows/publish.yml to replace "mirage" with "fair" in branch filters and build types. [1] [2]
• Updated .github/workflows/test.yml to rename "mirage" build jobs and commands to "fair."

Documentation Updates:

• Replaced all mentions of "Mirage" with "Fair" in README.md, including build type descriptions, commands, and usage examples. [1] [2] [3] [4] [5] [6] [7]

CLI Updates:

• Renamed node_cli/cli/mirage_boot.py and node_cli/cli/mirage_node.py to fair_boot.py and fair_node.py, respectively, and updated all references and command names from "mirage" to "fair." [1] [2] [3] [4] [5]

Versioning and Submodule:

• Incremented the project version from 3.0.0 to 3.1.0 in node_cli/cli/__init__.py.
• Updated the helper-scripts submodule to a new commit.