Lib_tar: add member path validation, bound raw allocation, and harden primitives

This MR adds validation of tar archive member names during snapshot import in both the L1 node and the smart rollup node. It also adds a regression test.

Manually testing the MR

dune exec src/lib_store/unix/test/main.exe -- --match "tar snapshot import rejects members with non-canonical paths"

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR