migrate containerd/pkg/tracing

[thaJeztah]

• stacked on ci: update actions and golangci-lint for go1.27, pin actions by sha #26
• also includes pkg/tracing: handle error and typed-nil Stringer attributes containerd#14013

migrate containerd/pkg/tracing

This migrates the log-related code from github.com/containerd/containerd/v2/pkg/tracing

Code was taken at this commit https://github.com/containerd/containerd/commits/fd399bd7b8cfdd47fb4f6cc021db417e5397a42f/pkg/tracing

Strategy taken:

# install filter-repo (https://github.com/newren/git-filter-repo/blob/main/INSTALL.md)
brew install git-filter-repo

cd ~/projects

# create a temporary clone of docker
git clone https://github.com/containerd/containerd.git tmp_tracing
cd tmp_tracing

git rev-parse HEAD
fd399bd7b8cfdd47fb4f6cc021db417e5397a42f

# remove all code, except for pkg/tracing, and rename to /otel
git filter-repo \
    --path tracing/helpers.go \
    --path tracing/log.go \
    --path tracing/log_test.go \
    --path pkg/tracing/helpers.go \
    --path pkg/tracing/log.go \
    --path pkg/tracing/log_test.go \
    --path-rename tracing/:otel/ \
    --path-rename pkg/tracing/:otel/ \
    --prune-empty always \
    --prune-degenerate always

# go to the target github.com/containerd/log repository
cd ~/projects/log

# create a branch to work with
git checkout -b integrate_tracing

# add the temporary repository as an upstream and make sure it's up-to-date
git remote add tmp_tracing ~/projects/tmp_tracing
git fetch --no-tags tmp_tracing main

# merge the upstream code
git merge --allow-unrelated-histories --signoff -S tmp_tracing/main

otel: fix imports, remove testify, add go.mod

Make the otel package a separate module, so that containerd/log
does not inherit the otel dependencies.

otel: handle error and typed-nil Stringer attributes

Log fields which contain an error currently fall through to JSON
marshaling, which may produce an unhelpful value such as "{}" instead
of the error message.

Handle error values explicitly and use fmt.Sprint when formatting error
and fmt.Stringer values. Besides preserving their textual
representation, fmt handles typed-nil implementations without
propagating a panic from their Error or String method.

Also simplify the final fmt.Sprintf("%v", v) fallback to fmt.Sprint(v).

[thaJeztah]

Oh! We need to update GolangCi lint, because it's now running go1.27

run golangci-lint
  Running [/home/runner/golangci-lint-2.12.2-linux-amd64/golangci-lint config path] in [/home/runner/work/log/log] ...
  Running [/home/runner/golangci-lint-2.12.2-linux-amd64/golangci-lint config verify] in [/home/runner/work/log/log] ...
  Running [/home/runner/golangci-lint-2.12.2-linux-amd64/golangci-lint run] in [/home/runner/work/log/log] ...
  Error: ../../../../../opt/hostedtoolcache/go/1.27.0/x64/src/internal/poll/splice_linux.go:237:21: unknown field rfd in struct literal of type splicePipe (typecheck)
  	return &splicePipe{rfd: fds[0], wfd: fds[1]}
  	                   ^