Convert Smarty & domain token processing to use token processor

[eileenmcnaughton]

Overview

Convert Smarty & domain token processing to use token processor

This is a subset of the changes in
#19550 that we should be able to resolve
& merge while addressing that takes longer. It still gets us the
benefit of adopting a preferred pattern

Before

Code uses older less preferred pattern

After

Code uses newer preferred pattern. In addition there is

1. less leakage around smarty variables
2. more consistency about handling of line breaks in subject lines (consistently converted to spaces with whitespace stripped from the end)

Technical Details

Note that some test changes exist around handling of subject -
the code now converts a new line to a space consistently. In addition
tests that rely on leakage have been altered as smarty does not leak with
this approach

Comments

[civibot]

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[eileenmcnaughton]

Thanks @mattwire I've rebased the other (of course the issues are still there with the other but they are clearer now)