rpk: fix $HOME-unset failures in OAUTHBEARER tests

config.Params.Load calls os.UserConfigDir, which requires $HOME to be
set. The Bazel sandbox does not set it. Add t.Setenv("HOME", "/") to
the loadProfile helpers so both `bazel test` and plain `go test` work.

Also add size="small" to the two new go_test targets; the default
MODERATE size was causing spurious Bazel warnings for sub-millisecond
tests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
(cherry picked from commit 9a73bbb)

Author: david-yu

src/go/rpk/pkg/kafka/BUILD

@@ -24,6 +24,7 @@ go_library(
 
 go_test(
     name = "kafka_test",
+    size = "small",
     srcs = ["client_franz_test.go"],
     embed = [":kafka"],
     deps = [

src/go/rpk/pkg/kafka/client_franz_test.go

@@ -21,6 +21,7 @@ import (
 // through the config system so internal fields are populated.
 func loadProfile(t *testing.T, fs afero.Fs, p *config.RpkProfile) *config.RpkProfile {
 	t.Helper()
+	t.Setenv("HOME", "/")
 	p.Name = "test"
 	rpkyaml := config.RpkYaml{
 		CurrentProfile: "test",

src/go/rpk/pkg/schemaregistry/BUILD

@@ -24,6 +24,7 @@ go_library(
 
 go_test(
     name = "schemaregistry_test",
+    size = "small",
     srcs = [
         "client_test.go",
         "context_test.go",

src/go/rpk/pkg/schemaregistry/client_test.go

@@ -21,6 +21,7 @@ import (
 // through the config system so internal fields are populated.
 func loadProfile(t *testing.T, fs afero.Fs, p *config.RpkProfile) *config.RpkProfile {
 	t.Helper()
+	t.Setenv("HOME", "/")
 	p.Name = "test"
 	rpkyaml := config.RpkYaml{
 		CurrentProfile: "test",