feat(multitenant): refactor multitenant to be multi-app configurable

[apeabody]

2-multitenant

• remove all hard coding for bank of anthos
• adds a new apps variable

variable "apps" {
  description = "Applications"
  type = map(object({
    ip_address_names = list(string)
  }))
}

• external ip addresses are now created based on ip_address_names in the new apps variable
• service accounts are now created for each app defined in the apps variable
• dynamic ip address test based on new global AppNames = []string testutils variable
• remove endpoints in favor of the updated dynamic ip address test
• dynamic service account test based on new global AppNames = []string testutils variable

[erictune]

Request adding documentation of what an App is. Other comments are optional to address in this PR or later.

[erictune]

LGTM based on #151