metricutil: switch to using the cli meter provider

The meter provider initialization that was located here has now been
moved to a common area in the docker cli. This upgrades our CLI version
and then uses this common code instead of our own version.

As a piece of additional functionality, the docker OTEL endpoint can now
be overwritten with `DOCKER_CLI_OTEL_EXPORTER_OTLP_ENDPOINT` for
testing.

This removes the OTLP exporter from the CLI that was previously locked
behind `BUILDX_EXPERIMENTAL`. I do plan for this to return, but as a
proper part of the `docker/cli` implementation rather than something
special with `buildx`.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

vendor/github.com/docker/cli/cli-plugins/hooks/printer.go

@@ -0,0 +1,18 @@
+package hooks
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/morikuni/aec"
+)
+
+func PrintNextSteps(out io.Writer, messages []string) {
+	if len(messages) == 0 {
+		return
+	}
+	fmt.Fprintln(out, aec.Bold.Apply("\nWhat's next:"))
+	for _, n := range messages {
+		_, _ = fmt.Fprintf(out, "    %s\n", n)
+	}
+}

vendor/github.com/docker/cli/cli-plugins/hooks/template.go

@@ -0,0 +1,115 @@
+package hooks
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"strconv"
+	"text/template"
+
+	"github.com/spf13/cobra"
+)
+
+type HookType int
+
+const (
+	NextSteps = iota
+)
+
+// HookMessage represents a plugin hook response. Plugins
+// declaring support for CLI hooks need to print a json
+// representation of this type when their hook subcommand
+// is invoked.
+type HookMessage struct {
+	Type     HookType
+	Template string
+}
+
+// TemplateReplaceSubcommandName returns a hook template string
+// that will be replaced by the CLI subcommand being executed
+//
+// Example:
+//
+// "you ran the subcommand: " + TemplateReplaceSubcommandName()
+//
+// when being executed after the command:
+// `docker run --name "my-container" alpine`
+// will result in the message:
+// `you ran the subcommand: run`
+func TemplateReplaceSubcommandName() string {
+	return hookTemplateCommandName
+}
+
+// TemplateReplaceFlagValue returns a hook template string
+// that will be replaced by the flags value.
+//
+// Example:
+//
+// "you ran a container named: " + TemplateReplaceFlagValue("name")
+//
+// when being executed after the command:
+// `docker run --name "my-container" alpine`
+// will result in the message:
+// `you ran a container named: my-container`
+func TemplateReplaceFlagValue(flag string) string {
+	return fmt.Sprintf(hookTemplateFlagValue, flag)
+}
+
+// TemplateReplaceArg takes an index i and returns a hook
+// template string that the CLI will replace the template with
+// the ith argument, after processing the passed flags.
+//
+// Example:
+//
+// "run this image with `docker run " + TemplateReplaceArg(0) + "`"
+//
+// when being executed after the command:
+// `docker pull alpine`
+// will result in the message:
+// "Run this image with `docker run alpine`"
+func TemplateReplaceArg(i int) string {
+	return fmt.Sprintf(hookTemplateArg, strconv.Itoa(i))
+}
+
+func ParseTemplate(hookTemplate string, cmd *cobra.Command) (string, error) {
+	tmpl := template.New("").Funcs(commandFunctions)
+	tmpl, err := tmpl.Parse(hookTemplate)
+	if err != nil {
+		return "", err
+	}
+	b := bytes.Buffer{}
+	err = tmpl.Execute(&b, cmd)
+	if err != nil {
+		return "", err
+	}
+	return b.String(), nil
+}
+
+var ErrHookTemplateParse = errors.New("failed to parse hook template")
+
+const (
+	hookTemplateCommandName = "{{.Name}}"
+	hookTemplateFlagValue   = `{{flag . "%s"}}`
+	hookTemplateArg         = "{{arg . %s}}"
+)
+
+var commandFunctions = template.FuncMap{
+	"flag": getFlagValue,
+	"arg":  getArgValue,
+}
+
+func getFlagValue(cmd *cobra.Command, flag string) (string, error) {
+	cmdFlag := cmd.Flag(flag)
+	if cmdFlag == nil {
+		return "", ErrHookTemplateParse
+	}
+	return cmdFlag.Value.String(), nil
+}
+
+func getArgValue(cmd *cobra.Command, i int) (string, error) {
+	flags := cmd.Flags()
+	if flags == nil {
+		return "", ErrHookTemplateParse
+	}
+	return flags.Arg(i), nil
+}