[nanvix] Wave 5 audit cleanup: drop dead helpers + tidy setup_local + enable inet_pton

[esaurez]

Three small upstream-alignment cleanups surfaced by the PR #20 audit against upstream cpython Linux's default .so management behavior. All are independent of each other and of the in-flight Wave 5 build chain -- pure dead-code / cosmetic removal.

Stacks on top of #20 (feat/wave5-pr-c-unbundle-group-a). Merge after #20 lands.

1. Makefile.nanvix: drop dead LIBSSL/LIBCRYPTO/LIBZ/LIBSQLITE3 vars

After Wave 5's Group-A unbundling these per-library .a path variables are no longer referenced anywhere -- the build picks up libssl / libcrypto / libz / libsqlite3 via -l<name> against the .so siblings in $(SYSROOT)/lib/. Removing the unused definitions makes it harder to accidentally reintroduce static linking by referencing one of them in a future LIBS rewrite.

2. .nanvix/config: drop dead toolchain_paths / configure_env helpers

Both helpers are unused: the actual cpython build invokes make -f Makefile.nanvix which has its own inline CONFIGURE_ENV authoritative for CC / CFLAGS / LDFLAGS / LIBS. The dead Python copies had drifted to stale pre-Wave-7 link flags (literal -lsqlite3 -lz -lbz2 -llzma in LIBS, no DT_NEEDED awareness) and would have mis-built any caller that picked them up. configure_opts() (still called from build.py) and the toolchain / docker path constants stay.

Closes the cleanup tracked in nanvix-todo/cpython-config-py-dead-configure-env.md.

3. .nanvix/setup_local: split POSIX-wrapper modules into their own section

Previously _asyncio, _datetime, select, _socket, _posixsubprocess, fcntl, and termios sat under the 'Modules with bundled-in-cpython C deps' section header, which is misleading -- none of them bundle a vendored .a; they are thin POSIX/syscall wrappers (plus _asyncio / _datetime) whose libc / libm symbols resolve against python.elf's .dynsym at dlopen time via --export-dynamic.

Move them into a dedicated 'POSIX syscall wrappers + concurrency primitives' section that mirrors upstream Modules/Setup.stdlib.in's 'Modules with some UNIX dependencies' grouping. Purely cosmetic -- no change to the generated Setup.local except entry order within the *shared* block (which makesetup does not depend on; each module name still appears at most once).

Validation

./z lint passes (black + pyright clean) after each commit.

Items NOT in this PR (deferred / blocked)

• B-1 (libm bundled into _decimal/pyexpat) -- upstream cpython hardcodes literal -lm in configure.ac:3918 and :3834 instead of using $(LIBM). Tracked separately for a future upstream PR against python/cpython.
• D-2 (unversioned SONAMEs) -- accepted as Nanvix convention.
• H-1 (ac_cv_func_inet_aton=no / inet_pton=no overrides may be stale) -- needs nm against libposix.a to confirm; tracked for follow-up.
• J-2 (--allow-multiple-definition on .so builds) -- blocked by B-1; once libm no longer gets bundled, the override can be scoped back to python.elf only.

[esaurez]

Update: added a 4th commit for audit finding H-1.

nm confirmed libposix.a defines inet_pton (T symbol), so the
ac_cv_func_inet_pton=no override in Makefile.nanvix was stale.
Flipped to =yes so cpython's configure sets HAVE_INET_PTON in
pyconfig.h, enabling the IPv6 fast paths and socket.inet_pton /
inet_ntop builtins in _socket.so. Symbol resolves via
python.elf .dynsym (libposix whole-archived + --export-dynamic).

inet_aton stays at =no -- not in libposix.

[esaurez]

Closing in favor of splitting these unrelated cleanups into four focused PRs (each independent, each based on feat/wave5-pr-c-unbundle-group-a):

• [nanvix] Makefile.nanvix: drop dead LIBSSL/LIBCRYPTO/LIBZ/LIBSQLITE3 vars #23 — Makefile.nanvix: drop dead LIBSSL/LIBCRYPTO/LIBZ/LIBSQLITE3 vars (C-1)
• [nanvix] .nanvix/config: drop dead toolchain_paths / configure_env helpers #24 — .nanvix/config: drop dead toolchain_paths / configure_env helpers (C-2)
• [nanvix] .nanvix/setup_local: split POSIX-wrapper modules into their own section #25 — .nanvix/setup_local: split POSIX-wrapper modules into their own section (A-2)
• [nanvix] Makefile.nanvix: enable ac_cv_func_inet_pton=yes #26 — Makefile.nanvix: enable ac_cv_func_inet_pton=yes (H-1)