[REF] Consistently lookup dispatcher via Civi::dispatcher()

[eileenmcnaughton]

Overview

Minor code standardisation

Before

We have are using 3 ways of getting the dispatcher

1. Civi\Core\Container::singleton()->get('dispatcher')
2. Civi::service('dispatcher')
3. Civi::dispatcher()

Tim confirms there is no functional difference

After

All instances call Civi::dispatcher()

Technical Details

From @totten on chat

"they're the same thing

Civi::dispatcher() is just a little prettier

e.g. the IDE is smarter about completing with ::dispatcher()

historically, ::service(...) was around before ::dispatcher()

and ::service(...) is a more generic facility.
you don't want to add every random little object as new wrapper method in Civi.php, but dispatcher is a really common+central thing"

Comments

From #16983 but I needed to clarify this & so doing did it throughout

[civibot]

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[seamuslee001]

Changes look fine to me merging