librz/core+bin: Remove obr (bin rebase command)

[thestr4ng3r]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository.
• I made sure to follow the project's coding style.
• I've documented every RZ_API function and struct this PR changes.
• I've added tests that prove my changes are effective (required for changes to RZ_API).
• I've updated the Rizin book with the relevant information (if needed).

Detailed description

Rebase done by obr freed all vfiles in the RzBinObject, but did not free
the entire RzBinFile, so core was not notified about it, and it may
still have had references to vfiles in vfile:// mappings, thus causing
UAFs.
Unfortunately the entire obr command was not working properly, so we
remove it with obR (also not entirely working) and rb being possible
replacements depending on the use-case.
The possibly dangerous RzBin apis have been made private in the module
to prevent future misuse.

Test plan

The following crashed before:

rz -c 'obl;obr 0x100000;obl' test/bins/elf/libmagic.so