Add an "incompatible" list to the ExtendedConfigKey

[Claudenw]

Current state

The ExtendedConfigKey was introduced in v2.9.0 to allow us to extend the definitions of configuration items for documentation purposes. To this end we added:

• since to track when a configuration option was added.
• deprecated to provide deprecation information.

Proposed change.

Add incompatible as as a list of Strings similar to the ConfigKey.dependents. The intention being to indicate which values can not be set when other values are set. Setting A as incompatible with B will imply that B is incompatible with A.

The changes are required in

• ExtendedConfigKey and its Builder to define and store the data.
• ExtendedConfigKeyBean to retrieve the data.
• BigQueryConfigDefBean to retrieve the ConfigKey's that are incompatible with a specified ConfigKey.
• configuration.md.vm to format and present the data.

Since this is a bidirectional property, the BigQueryConfigDefBean retrieval should search the incompatibilities explicitly listed in the ConfigKey as well as any ConfigKey that list incompatibilities with the specified ConfigKey.