New email design for dashboard subscriptions, alerts and pulses (#17781)

...e/backend/test/metabase_enterprise/sandbox/pulse_test.clj

frontend/src/metabase/pulse/components/PulseEditCards.jsx

src/metabase/email/_footer.mustache

src/metabase/email/_footer_pulse.mustache

src/metabase/email/alert.mustache

src/metabase/email/messages.clj

src/metabase/email/pulse.mustache

src/metabase/pulse.clj

src/metabase/pulse/markdown.clj

src/metabase/pulse/render.clj

src/metabase/pulse/render/body.clj

src/metabase/pulse/render/js_svg.clj

src/metabase/pulse/render/style.clj

src/metabase/util/quotation.clj

src/metabase/util/urls.clj

test/metabase/dashboard_subscription_test.clj

test/metabase/email_test.clj

test/metabase/pulse/test_util.clj

test/metabase/pulse_test.clj