Add W7900 GPU support to build system

Add AMD Radeon PRO W7900 (gfx1100) GPU support to the Bazel build system
by adding amdgpu:gfx1100 to the supported_gpus dictionary.

Update bazel/common.MODULE.bazel to include "W7900": "amdgpu:gfx1100" in
the supported_gpus dictionary and add GPU detection mappings for both
"AMD Radeon PRO W7900" and "AMD Radeon Pro W7900" (case variants).
Make generic Navi GPU mappings more specific to avoid conflicts.

The gfx1100 architecture itself was already supported in the Mojo codebase
via sys.info._is_amd_rdna3() which includes gfx1100, but the W7900 GPU
name was missing from the build system's supported GPU list.

Author: mcgrof

bazel/common.MODULE.bazel

@@ -301,9 +301,11 @@ mojo.gpu_toolchains(
         "MI300X": "mi300x",
         "MI325": "mi325",
         "MI355": "mi355",
-        "Navi": "radeon",
-        "AMD Radeon Graphics": "radeon",
+        "Navi 31": "W7900",
+        "Navi 31 [Radeon Pro W7900]": "W7900",
         "AMD Radeon RX 6900 XT": "rx6900xt",
+        "AMD Radeon PRO W7900": "W7900",
+        "AMD Radeon Pro W7900": "W7900",
         "Metal 1": "",  # Unsupported, macOS updates on any hardware get you to Metal 3+
         "Metal 2": "",  # Unsupported, macOS updates on any hardware get you to Metal 3+
         "Metal 3": "metal3",  # macOS 15
@@ -312,6 +314,7 @@ mojo.gpu_toolchains(
     # GPU name -> target accelerator
     supported_gpus = {
         "780M": "amdgpu:gfx1103",
+        "W7900": "amdgpu:gfx1100",
         "a10": "nvidia:86",
         "a100": "nvidia:80",
         "a3000": "nvidia:86",