os/bluestore: Add UT for ExtentMap::dup_esb()

os/bluestore: Add UT for ExtentMap::dup_esb()

Add unit tests for ExtentMap::dup_esb() to test_bluestore_types.
Extra hooks added to BlueStore:
1) bluestore_extent_ref_map_t::debug_peek inspects how many times specific AU is used
2) ExtentMap::debug_list_disk_layout to extract how onode maps to AUs
3) BlueStore::debug_punch_hole to use logic from _wctx_finish internal function

Unit tests are limited to operations aligned to allocation unit.

Signed-off-by: Adam Kupczyk <akupczyk@ibm.com>