Switch to use laminas/laminas-mail instead of zendframework/zend-mail

[glensc]

https://github.com/zendframework/zend-mail repository was abandoned on 2019-12-31

Previously we maintained zend-mail fork, because upstream was unacceptably slow to accept pull requests and make a release:

• https://github.com/eventum/zend-mail: This branch is 11 commits ahead, 14 commits behind zendframework:master.

there's 2.10.1 released for laminas-mail that still does not contain the fixes:

• #83 fixes PHPDocs in Transport\InMemory (the last message can be null).
• #84 fixes PHP 7.4 compatibility.
• #82 fixes numerous issues in Storage\Maildir. This storage adapter was not working before and unit tests were disabled.
• #75 fixes how Laminas\Mail\Header\ListParser::parse() parses the string with quotes.
• #88 fixes recognizing encoding of Subject and GenericHeader headers.

the version we used was branched of 2.10.0, with following backports:

• Treat quote as value if already in quote using another delimiter zendframework/zend-mail#226 fixed in Treat quote as value if already in quote using another delimiter laminas/laminas-mail#75
• Fix AddressList toString method to quote semicolon zendframework/zend-mail#230 will be fixed in Fix AddressList toString method to quote semicolon laminas/laminas-mail#93