Migrate to `-pr:a` for target profiles

[kammce]

Now that Conan supports conan-io/conan#18383, we can start adding build profile context and options into our profiles.

The docs that should be changes are:

1. Usage of previously host profile will now be a dual host/build profile (still called a target or host profile)
2. Switch from v1 libhal-arm-mcu conan profiles to v2.
3. Users must use -pr:a for their build targets such as lpc4078 would be conan build app -pr:a lpc4078