Feature/apk software inventory

[Megachip]

Add software inventory support for Alpine Package Keeper (apk)

Closes the request in discussion #901.

Why

Alpine Linux is the default distribution for a large share of Docker base
images, but glpi-agent had no software-inventory support for its package
manager apk. Installed apk packages were therefore missing from the
inventory entirely.

What

New module GLPI::Agent::Task::Inventory::Generic::Softwares::APK.

It reads the apk installed packages database (/lib/apk/db/installed)
directly rather than forking the apk binary. This was chosen over parsing
apk list --installed output because it is:

• faster — a single file read instead of spawning apk, which parses that
  very same file itself;
• more robust — the package name and version are stored in separate
  fields (P: / V:), so there is no fragile name-version token splitting
  (apk names may contain digits, e.g. libcrypto3, which makes heuristic
  splitting error-prone). This also sidesteps the apk v2/v3 list output
  differences raised in the discussion;
• richer — installed size and description are available in the same pass.

The database describes each package as a block of key:value lines separated
by a blank line. The module extracts:

apk field	GLPI field
P	NAME
V	VERSION
A	ARCH
I	FILESIZE (installed size, in bytes)
T	COMMENTS (description)
m	PUBLISHER (maintainer, when present)
—	FROM => 'apk'

isEnabled() requires both canRun('apk') and the database file to be present.
Maintainer names are UTF-8 decoded (like the RPM module). INSTALLDATE is
deliberately not set: the database only stores the package build time (t:),
not a per-host installation date (the Deb module omits it for the same reason).

Tests

• Added fixture resources/linux/packaging/apk (a realistic installed
  database, incl. a multi-hyphen name, a digit-suffixed name libcrypto3, a
  noarch package and one package without a maintainer field).
• Extended t/tasks/inventory/linux/softwares.t with apk parsing and
  registration checks. Full file passes (27/27). use utf8 was added so the
  accented maintainer names in the expectations compare correctly.

Notes

• opkg is intentionally out of scope here and can follow in a separate PR.
• apk-tools 3 will move the installed database to a binary ADB format; when that
  reaches stable Alpine, the parser will need a format check. All currently
  deployed Alpine releases use the text format handled here.