[CT-2847] Apply more consistent formatting to exception from dbtPlugin.initialize

[MichelleArk]

dbtPlugin.initialize should be used to encapsulate any setup necessary to successfully call hook methods. It should be expected by dbt-core that some error handling is necessary there, and sensible-looking error messages be logged. Currently, any exception from a dbtPlugin.initialize method is pretty verbose and exposes unnecessary details about the plugin method:

❯ dbt run
20:30:47  Running with dbt=1.7.0-a1
20:30:47  target not specified in profile 'postgres', using 'default'
20:30:47  Encountered an error:
Runtime Error
  initialize: Runtime Error
    custom error message

On the other hand, the existing dbt_hooks (get_nodes and get_manifest_artifact) aren't expected to raise exceptions assuming proper initialization - so dbt-core can more aggressively handle exceptions from hooks (at least for now!). So they are fine as-is.

Exit Criteria: exceptions raised by dbtPlugin.initialize should be formatted to look more inline with what a user would expect from a regular user-facing dbt-core exception.