[build] Move to python build scripts per module

This change moves Bonnibel from a separate project into the jsix tree,
and alters the project configuration to be jsix-specific. (I stopped
using bonnibel for any other projects, so it's far easier to make it a
custom generator for jsix.) The build system now also uses actual python
code in `*.module` files to configure modules instead of TOML files.
Target configs (boot, kernel-mode, user-mode) now moved to separate TOML
files under `configs/` and can inherit from one another.

src/boot/boot.module

@@ -0,0 +1,22 @@
+# vim: ft=python
+
+module("boot",
+    kind = "exe",
+    output = "boot.efi",
+    targets = [ "boot" ],
+    deps = [ "cpu", "elf", "kutil" ],
+    sources = [
+        "allocator.cpp",
+        "console.cpp",
+        "error.cpp",
+        "fs.cpp",
+        "hardware.cpp",
+        "loader.cpp",
+        "main.cpp",
+        "memory.cpp",
+        "memory_map.cpp",
+        "paging.cpp",
+        "status.cpp",
+        "support.cpp",
+        "video.cpp",
+    ])

src/boot/module.toml

@@ -1,20 +0,0 @@
-name = "boot"
-kind = "exe"
-output = "boot.efi"
-targets = ["boot"]
-deps = ["cpu", "elf", "kutil"]
-sources = [
-	"allocator.cpp",
-	"console.cpp",
-	"error.cpp",
-	"fs.cpp",
-	"hardware.cpp",
-	"loader.cpp",
-	"main.cpp",
-	"memory.cpp",
-	"memory_map.cpp",
-	"paging.cpp",
-	"status.cpp",
-	"support.cpp",
-	"video.cpp",
-]