feat(users/flokli/kb): add chocofi

`buildSplitKeyboard`, as well as all the patching of `miryoku_zmk` is
independent of the specific keyboard used, so it can be moved one layer
up.

`config-flat` is now provided through a helper function, accepting the
name of the keymap to use when rendering the config.

This all makes the amount of code added for the new keyboard itself
pleasantly small.

Change-Id: I2216aa246502eddaf9bc4f4d126b0639d574ad87
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12787
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

users/flokli/keyboards/west.yml

@@ -0,0 +1,34 @@
+manifest:
+  remotes:
+    - name: zmkfirmware
+      url-base: https://github.com/zmkfirmware
+  projects:
+    - name: zephyr
+      remote: zmkfirmware
+      revision: f8e4d15791602c67405c0fd2651167a895939565  # v3.5.0+zmk-fixes
+      import:
+        name-blocklist:
+          - ci-tools
+          - hal_altera
+          - hal_cypress
+          - hal_infineon
+          - hal_microchip
+          - hal_nxp
+          - hal_openisa
+          - hal_silabs
+          - hal_xtensa
+          - hal_st
+          - hal_ti
+          - loramac-node
+          - mcuboot
+          - mcumgr
+          - net-tools
+          - openthread
+          - edtt
+          - trusted-firmware-m
+    - name: zmk
+      remote: zmkfirmware
+      revision: 7f1ee320ab638245bbdae9b1cda5d5c50e2cb16e  # main
+      import: app/west.yml
+  self:
+    path: config