bazel, bazel_5, bazel_6, bazel_7: move to pkgs/by-name/ba/

[boltzmannrain]

Mostly a pure move keeping pkgs/top-level darwin overrides.
Shared files from pkgs/development/tools/build-managers/bazel/ are copied to each bazel_{version] that uses them instead of figuring out the way to keep sharing. Patch sharing is of limited value, tests sharing looks more reasonable but bazel_7 (or upcoming bazel_8) doesn't use those tests and a new test setup would need to be implemented anyway.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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