Change `partition_autobalancing_mode` to `continous` upon applying enterprise license

[daisukebe]

Who is this for and what problem do they have today?

Once a Redpanda enterprise user applies a valid license, we allow them to use the enterprise features listed here, https://docs.redpanda.com/current/get-started/licenses/#redpanda-enterprise-edition.

Most of them are what users should explicitly configure but the Continuous Data Balancing should be turned on automatically because it just gives users advantages.

What are the success criteria?

• Apply a valid enterprise license
• Automatically change partition_autobalancing_mode to continuous
• Let the user know what are changed in the rpk command output

Why is solving this problem impactful?

• Prevent partition skews on addition of nodes from happening

Additional notes

I've got +1 from @mattschumpert in https://redpandadata.slack.com/archives/C03GJ5HV8P9/p1704384519063189

JIRA Link: CORE-1700

[mattschumpert]

+1

[mattschumpert]

FYI @michael-redpanda