nfc_util: little endian bytes2num functions added

[Leptopt1los]

What's new

• nfc_util_bytes2num_little_endian function added

Problem:
When developing parsers, i often come across cards in which data is stored in little endian. in nfc_util.c there is a function uint64_t nfc_util_bytes2num(const uint8_t* src, uint8_t len), which reads len bytes at the src pointer and returns them as a number. The problem is that it reads them as big endian, and there is no alternative. Accordingly, for each such case I have to write an extra loop and read everything manually

This feature will solve the problem

Verification

• test that the function does not go beyond boundaries
• test the correctness of operation (the result is indeed a representation of the little endian number stored in the src)

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix

[hedger]

Please sync changes across all targets (./fbt TARGET_HW=18).

[Leptopt1los]

Please sync changes across all targets (./fbt TARGET_HW=18).

done

done