machine/stm32: add STM32U585 target definition and runtime

Add processor target (cortex-m33), linker script (2048K flash, 768K RAM),
and arduino-uno-q board target. Runtime initializes 160MHz clock via PLL1
from HSI16, with PWR Range 1 and EPOD booster.

Also add psctype abstraction for timer PSC register width, needed because
the U5 SVD defines PSC as a 16-bit register.

targets/stm32u585.json

@@ -0,0 +1,16 @@
+{
+  "inherits": [
+    "cortex-m33"
+  ],
+  "build-tags": [
+    "stm32u585",
+    "stm32u5",
+    "stm32"
+  ],
+  "extra-files": [
+    "src/device/stm32/stm32u585.s"
+  ],
+  "linkerscript": "targets/stm32u585.ld",
+  "flash-method": "openocd",
+  "openocd-target": "stm32u5x"
+}