feat(coderd): add matched provisioner daemons information to more places (#15688)

- Refactors `checkProvisioners` into `db2sdk.MatchedProvisioners`
- Adds a separate RBAC subject just for reading provisioner daemons
- Adds matched provisioners information to additional endpoints relating to
  workspace builds and templates
-Updates existing unit tests for above endpoints
-Adds API endpoint for matched provisioners of template dry-run job
-Updates CLI to show warning when creating/starting/stopping/deleting
 workspaces for which no provisoners are available

---------

Co-authored-by: Danny Kopping <danny@coder.com>

cli/cliutil/provisionerwarn.go

@@ -0,0 +1,53 @@
+package cliutil
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/coder/coder/v2/cli/cliui"
+	"github.com/coder/coder/v2/codersdk"
+)
+
+var (
+	warnNoMatchedProvisioners = `Your build has been enqueued, but there are no provisioners that accept the required tags. Once a compatible provisioner becomes available, your build will continue. Please contact your administrator.
+Details:
+	Provisioner job ID : %s
+	Requested tags     : %s
+`
+	warnNoAvailableProvisioners = `Provisioners that accept the required tags have not responded for longer than expected. This may delay your build. Please contact your administrator if your build does not complete.
+Details:
+	Provisioner job ID : %s
+	Requested tags     : %s
+	Most recently seen : %s
+`
+)
+
+// WarnMatchedProvisioners warns the user if there are no provisioners that
+// match the requested tags for a given provisioner job.
+// If the job is not pending, it is ignored.
+func WarnMatchedProvisioners(w io.Writer, mp *codersdk.MatchedProvisioners, job codersdk.ProvisionerJob) {
+	if mp == nil {
+		// Nothing in the response, nothing to do here!
+		return
+	}
+	if job.Status != codersdk.ProvisionerJobPending {
+		// Only warn if the job is pending.
+		return
+	}
+	var tagsJSON strings.Builder
+	if err := json.NewEncoder(&tagsJSON).Encode(job.Tags); err != nil {
+		// Fall back to the less-pretty string representation.
+		tagsJSON.Reset()
+		_, _ = tagsJSON.WriteString(fmt.Sprintf("%v", job.Tags))
+	}
+	if mp.Count == 0 {
+		cliui.Warnf(w, warnNoMatchedProvisioners, job.ID, tagsJSON.String())
+		return
+	}
+	if mp.Available == 0 {
+		cliui.Warnf(w, warnNoAvailableProvisioners, job.ID, strings.TrimSpace(tagsJSON.String()), mp.MostRecentlySeen.Time)
+		return
+	}
+}