updatehub: 2.1.5 -> 2.1.6

[otavio]

Bumps the updatehub agent recipe to the 2.1.6 release.

SRCREV points at b56a988b168e52e4822829a4a2cb4880a6f80f2b, the commit tagged 2.1.6.

updatehub-crates.inc was regenerated from the new Cargo.lock; the notable
deltas are bindgen 0.59.2 -> 0.69.5 and loopdev 0.4.0 -> loopdev-3 0.5.1 (a
dev-dependency), plus the transitive bitflags 2.x and windows-sys 0.52.6 pickups
they drag in. No new build-time dependencies, so DEPENDS is unchanged, and the
v1-parsing feature backing PACKAGECONFIG[backward-compatibility] is still
declared upstream.

Testing

Built for qemuarm against oe-core master: do_fetch, do_compile,
do_package_qa and ipk packaging all succeed. LIC_FILES_CHKSUM still matches
upstream LICENSE-APACHE.

Backports to whinlatter, walnascar, scarthgap and kirkstone follow once this lands.

[github-actions]

Backport failed for kirkstone, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin kirkstone
git worktree add -d .worktree/backport-116-to-kirkstone origin/kirkstone
cd .worktree/backport-116-to-kirkstone
git checkout -b backport-116-to-kirkstone
ancref=$(git merge-base 28393e07be03c9554f8add3f4982b658b47d5d94 0272cd5cf7d7a2ff6bec1f943e56069d33204df3)
git cherry-pick -x $ancref..0272cd5cf7d7a2ff6bec1f943e56069d33204df3

[github-actions]

Backport failed for scarthgap, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin scarthgap
git worktree add -d .worktree/backport-116-to-scarthgap origin/scarthgap
cd .worktree/backport-116-to-scarthgap
git checkout -b backport-116-to-scarthgap
ancref=$(git merge-base 28393e07be03c9554f8add3f4982b658b47d5d94 0272cd5cf7d7a2ff6bec1f943e56069d33204df3)
git cherry-pick -x $ancref..0272cd5cf7d7a2ff6bec1f943e56069d33204df3

[github-actions]

Backport failed for walnascar, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin walnascar
git worktree add -d .worktree/backport-116-to-walnascar origin/walnascar
cd .worktree/backport-116-to-walnascar
git checkout -b backport-116-to-walnascar
ancref=$(git merge-base 28393e07be03c9554f8add3f4982b658b47d5d94 0272cd5cf7d7a2ff6bec1f943e56069d33204df3)
git cherry-pick -x $ancref..0272cd5cf7d7a2ff6bec1f943e56069d33204df3

[github-actions]

The process '/usr/bin/git' failed with exit code 1