[Darwin] Fix incorrect Thread panID generation

[sagar-apple]

Problem

The underlying cpp implementation assumes(with no documentation) that the input panID is meant to be in Big-Endian.

Change overview

Explicitly convert from Host order to BE when constructing the underlying cpp structure. And make sure to convert back into Host order when pulling information out of a buffer again.

Testing

How was this tested? (at least one bullet point required)

• If unit tests were added, how do they cover this issue?
  Added a unit test to convert individual fields to a data buffer and then reconstruct the individual fields from that data buffer

[github-actions]

Size increase report for "esp32-example-build" from c4fe313

File	Section	File	VM
chip-lock-app.elf	.flash.text	-64	-64

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-lock-app.elf and ./pull_artifact/chip-lock-app.elf:

sections,vmsize,filesize
[Unmapped],0,64
.flash.text,-64,-64

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-ipv6only-app.elf and ./pull_artifact/chip-ipv6only-app.elf:

sections,vmsize,filesize