Debugger: introduce target endianness handling

Change-Id: I597a667de1461383ce9e96e8ea9902895cf80ec6
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7073
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

Debugger: implement parsing DW_FORM_implicit_const

For attributes with form DW_FORM_implicit_const, the attribute
specification contains a third part which is a signed LEB128
number. This value shall be used as the value of the attribute
when parsing the debug_info section.

Change-Id: I3e9aa3ba70b3aa05e6d2f570a1464966c38e4b1b
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6980
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Rene Gollent <rene@gollent.com>

Debugger: Fix #13939, more work on #13800.

- Fix various cases where OpenHashTables weren't being cleared properly.
- Fix various reference counting errors.
- Simplify FileManager reference handling.
- Fix bug in LocatableDirectory where the directory named '/' would have its
name returned as empty. This would lead to failed lookups for entries already
in the table, and ultimately corrupted the hash table when deleting unused
entries, leading to #13939. This was previously never noticed due to the
entries not being freed properly.
- AbbreviationTable wasn't clearing its entries.

Debugger: Split into core library and application.

- Add subfolder src/kits/debugger which contains the debugger's core
functionality and lower layers. Correspondingly add headers/private/debugger
for shared headers to be used by clients such as the Debugger application
and eventual remote_debug_server. Adjust various files to account for
differences as a result of the split and moves.
- Add libdebugger.so to minimal Jamfile.