Add xtask command to generate and verify flash image

Following the flash layout defined in
https://github.com/chipsalliance/caliptra-mcu-sw/blob/main/docs/src/flash_layout.md

- Add new command to specify the firmware files and soc manifest to
create 1 flash image file that can be burned to the SPI flash.

- Add new command to verify a flash image file

Example:

cargo run --bin flash-image create --caliptra-fw caliptra_fw.bin \
             --soc-manifest soc_manifest.bin \
             --mcu-runtime mcu_runtime.bin \
             --soc-images soc_image1.bin soc_image2.bin soc_image3.bin \
             --output flash_image.bin

cargo run --bin flash-image verify flash_image.bin

xtask/Cargo.toml

@@ -13,3 +13,4 @@ clap.workspace = true
 registers-generator.workspace = true
 registers-systemrdl.workspace = true
 quote.workspace = true
+crc32fast = "1.4.2"