Odoo Release Updates

[IMP] mail,*: MailThreadCC removal, default subject and tweaks

[IMP] utm: improve and generalize UTM trackers data

[IMP] mass_mailing, *: add auto-fill snippet plugin

[IMP] mass_mailing: Simplifying merge action

[REF] html_editor, *: turn normalize_handlers into processors

[REF] html_editor, *: turn clean_for_save_handlers into processors

[REF] html_editor, *: turn a few more handlers into processors

[IMP] mail: cleanup track naming and usage

[REF] *: remap reactive import to owl2/utils

[REF] *: remap useState import to owl2/utils

[REF] *: remap useRef import to owl2/utils

[REF] *: remap useSubEnv import to owl2/utils

[REF] *: remap useComponent import to owl2/utils

[FIX] mass_mailing: unlink mail.message of test mails

[REF] *: Replace useEffect with useLayoutEffect for owl3 migration

[IMP] base_import, *: comprehensive UX cleanup and modernization

[FIX] mass_mailing: handle reviews wall crash

[IMP] mass_mailing: add new snippets

[CLN] *: clean UTM demo data

[FIX] mass_mailing: prevent blockquote content loss

[REF] test_mail, various: cleanup tracking tests

[IMP] various: update mail track tests

[FIX] mass_mailing: fix columns block layout in received emails

[IMP] *: rename "Cancel" to "Discard"

[IMP] *: remove datas

[FIX] mass_mailing: don't enforce deep font-family

[FIX] *: replace "Deco Addict" with "Acme Corporation"

[IMP] mass_mailing: remove Design Tab --link-font-size

[FIX] website, html_builder, mass_mailing: register snippet models

[FIX] mass_mailing: fix non-deterministic errors