[FEATURE] Allow building nxboot, miniboot or NuttX mcuboot on esp32

### Is your feature request related to a problem? Please describe.

Building nxboot, miniboot or the NuttX port of mcuboot fails on esp32 because `int board_boot_image(const char *path, uint32_t hdr_size)` is not implemented for esp32.

### Describe the solution you'd like

Provide a `int board_boot_image(const char *path, uint32_t hdr_size)` for the different types of images that are supported by esp32 NuttX. This could be limited to the simpleboot and mcuboot image formats, and return `-ENOTSUP` for the legacy format.

When this functionality is provided it would remove the need to build the espressif port of mcuboot. It would also allow building miniboot, nxboot or other future bootloaders that are NuttX based. I have tried to distill such a functionality from the espressif port of mcuboot but I think that the there used solution is having some intrinsic limitations introduced by the hardware setup.

### Describe alternatives you've considered

_No response_

### Verification

- [x] I have verified before submitting the report.