Prepares the move of ICP to mail before replacing them by dynamic alias
domains. Improve test coverage, notably for edge cases. Continue to make
tests more explicit after odoo/odoo#131492. Some tests are also merged to
lessen number of different tests when possible, notably when only a test
parameter differs (like giving an SMTP session or not).
Clean ICP and mail servers setup in test classes allowing to remove some
unnecessary extra initialization. Cleanup a mock in mail.
Task-3453347 (Mail: Move Mail ICP from Base to Mail)
Prepares Task-36879 (Mail: Support MultiCompany Aliases)
Part-of: odoo/odoo#130750
Thibault Delavallée
17e5bbb38b