i18n: add e2e tests in plugin-e2e

[hugohaggmark]

It's time to add some basic smoke e2e tests for the i18n stuff in plugins

For each test case below we need to test the following behavior:

• test an English label in Grafana >=12.1.0, should just work
• test an English label in Grafana >= 11.0.0 < 12.1.0, should just work
• test a Spanish label in Grafana >=12.1.0, should just work
• test a Spanish label in Grafana >= 11.0.0 < 12.1.0, should just work
• test a Swedish label in Grafana >=12.1.0, should just work
• test a Swedish label in Grafana >= 11.0.0 < 12.1.0, should default to English

Test cases

• e2e test for a translated panel plugin
• e2e test for a translated data source plugin
• e2e test for a translated app plugin
• e2e test for a translated scenes app plugin