Multiple feature parity issues with essentials subcription and database resources

[briankzimmer]

I've left out a number of sections in the default template, as I think the issue is pretty clear even from just reading the documentation for the provider. LMK if more details are needed, though.

Affected Resource(s)

Please list the resources as a list, for example:

• rediscloud_essentials_subscription
• rediscloud_essentials_database

Expected Behavior

• rediscloud_essentials_subscription should support setting payment_method = "marketplace" in the same way that rediscloud_subscription does
• rediscloud_essentials_database should set a db_id attribute in the same way that rediscloud_subscription_database does

There may be a few more inconsistencies, but these are the ones blocking me.

Actual Behavior

The opposite of every case above.