http_block: use generic block component/driver

Ref #966
http_block: rename to http_blk to be consistent

Ref #966
rom_blk test: abort if test fails

Instead of printing the success message at the end of the test,
abort as soon as two blocks differ.

Ref #966
http_blk: use libc_lwip plugin, not lwip directly

Ref #966
http_blk: add run script for automated tests

Ref #966