vendor: update buildkit to v0.12.0, containerd v1.7.2

[thaJeztah]

vendor: github.com/containerd/containerd v1.7.2

full diff: https://github.com/containerd/containerd/compare/v1.6.21..v1.7.2

vendor: github.com/moby/buildkit v0.12.0

full diff: https://github.com/moby/buildkit/compare/v0.11.6..v0.12.0

- A picture of a cute animal (not mandatory but encouraged)

[thaJeztah]

Actually, let me keep this as draft, and only update the (indirect) dependencies for now.

We don't necessarily need the buildkit update on the client-side, which could allow us to stick to containerd 1.6 (LTS) potentially?

The only parts of BuildKit used are;

tree vendor/github.com/moby/buildkit
vendor/github.com/moby/buildkit
├── AUTHORS
├── LICENSE
├── frontend
│ └── dockerfile
│ └── dockerignore
│ └── dockerignore.go
└── util
├── appcontext
│ ├── appcontext.go
│ ├── appcontext_unix.go
│ ├── appcontext_windows.go
│ └── register.go
└── bklog
└── log.go
6 directories, 8 files

[codecov-commenter]

Codecov Report

Merging #4455 (b809cec) into master (8837d11) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@ Coverage Diff @@## master #4455 +/- ##
=======================================
Coverage 59.39% 59.39% =======================================
Files 288 288 Lines 24782 24782 =======================================
Hits 14720 14720 Misses 9175 9175 Partials 887 887 

[thaJeztah]

closing in favour of #4605