build(macos): inline homebrew deps in setup script, drop px4-dev meta-formula

Homebrew 4.5 (April 2026) stopped auto-tapping cross-tap
dependencies declared in formulae, as a security + performance
change. The px4-dev meta-formula pulled in packages from
osx-cross/arm, PX4/px4, and discoteq/discoteq, so 'brew install
px4-dev' now aborts before any real work unless every tap has been
added explicitly. On macos-latest CI runners the chain broke at the
first unreachable dep (discoteq/discoteq/flock) and subsequent make
steps failed with 'ccache: command not found'.

Since Tools/setup/macos.sh is the canonical install path and already
tapped osx-cross/arm and PX4/px4 before calling brew install, the
simplest fix is to inline the package list and call brew install
directly. The px4-dev meta-formula will be kept upstream as a
deprecated no-op so older copies of macos.sh on long-lived branches
and cached Docker images keep working.

The inlined package list is the same set px4-dev depended on, minus
the dead-weight flock dependency that hadn't been invoked in the PX4
build since the NuttX 9.1.x era. See the accompanying PX4/homebrew-px4
PR for formula changes.

Docs updated to match: docs/en/dev_setup/dev_env_mac.md no longer
names the px4-dev formula, describes the package list directly.

Verified locally on macOS ARM64:
- ./Tools/setup/macos.sh runs to completion with both taps and all 13
  packages resolving correctly
- make distclean && make px4_fmu-v6x_default builds successfully
  (1250/1250 ninja steps, 1930096 B FLASH used)

Signed-off-by: Ramon Roche <mrpollo@gmail.com>

docs/en/dev_setup/dev_env_mac.md

@@ -59,7 +59,7 @@ To build for [other targets](../dev_setup/dev_env.md#supported-targets) you will
    ```
 
    This installs:
-   - **`px4-dev`** — ARM cross-compiler (`arm-gcc-bin@13`), `cmake`, `ninja`, `ccache`, and other build tools
+   - **Toolchain packages** from the `osx-cross/arm` and `PX4/px4` Homebrew taps — ARM cross-compiler (`arm-gcc-bin@13`), `cmake`, `ninja`, `ccache`, `fastdds`, `genromfs`, `kconfig-frontends`, and other build tools
    - **Python packages** from `requirements.txt`
    - **`px4-sim`** (via `--sim-tools`) — Gazebo Harmonic simulation (`gz-harmonic`) and related tools