Odoo Release Updates

[FIX] mass_mailing: inline placeholder element

[CLN] *: manifests

[IMP] html_builder, mass_mailing, website: add slider to resize media

[IMP] *: add social account snippet in mass mailing

[FIX] mass_mailing: prevent error on selecting mail template

[FIX] *: automaticaly set legacy at_install

[IMP] web: cache identical name_search calls in M2X

[IMP] mass_mailing: handle visual assets in builder

[FIX] html_editor, mass_mailing, website: fix background repeat pattern

[FIX] web,*: RPCCache: correctly handle rejected promises

[FIX] mass_mailing: add mail contact to mail list through wizard

[FIX] mass_mailing: post-refactoring follow-up fixes

[IMP] mass_mailing, web: add conditional visibility on snippets

[FIX] mass_mailing: inline placeholder elements

[FIX] mass_mailing: prevent infinite scrolling when viewing mails

[FIX] mass_mailing: display mailings without body_arch in readonly

[REF] html_builder, *: move back builder-specific scss to html_builder

[REF] all: model's description should be singular

[FIX] mass_mailing: fix separator title snippet

[FIX] mass_mailing: remove erroneous mass_mailing style

[FIX] mass_mailing: use o_mail_no_colorpicker instead of s_col_no_bgcolor

[FIX] mass_mailing: remove empty containers and sections

[FIX] mass_mailing(_themes): increment mass_mailing snippets vxml

[FIX] mass_mailing: align fontFamilyPicker option

[REF] *: use ir.config_parameter new API get_xxx, set_xxx

[IMP] base,all: remove deprecated 't-esc' ir.qweb directive

[FIX] mass_mailing: retry failed emails in batches

[FIX] mass_mailing: fix theme selector favorite template star color

[FIX] mass_mailing: fix html_editor test helpers not present in single app

[FIX] mass_mailing: restore template model-lock