tests/periph_flashpage: add automated test for flash peripheral

[fedepell]

Contribution description

Add a simple automatic test for flash peripheral as discussed in #10069. The test will do an erase/write/read/compare cycle using the flashpage_write_and_verify() function on the last page of the flash available. The last page is used to try to be hardware independant.

Testing procedure

Execute:

make flash test

in tests/periph_flashpage

Issues/PRs references

As discussed in #10069 to test the proposed PR.

[aabadie]

Thanks @fedepell, it looks good and exactly what is required.
It could still be further improved by also testing the flashpage_raw feature but that could be done in a follow-up (except if you want to look at that here).

Also tested and works as expected.

[fedepell]

@aabadie : thanks for the feedback! I fixed the printf/puts, thanks!

I'll check flashpage_raw now!

[fedepell]

@aabadie : I added a test also for a short write with flashpage_raw. As this is not supported by all HW the test first checks if it is available (by checking help contents) and then calls it eventually. I added a new command in the shell for simplicity, not to have to do a too long parsing to calculate the last page.

[aabadie]

Code changes are good. Nothing to say there.

I tested this PR on several IoT-LAB nodes (samr21, st-lrwan1, m3, arduino-zero) and all have passed.

ACK

[aabadie]

All CI are green, let's merge. Thanks @fedepell, this is very useful!