Move shared components to a packages/ directory (#30962)

* Move shared components to a packages/ directory

so they can be publish more sensibly

* Iterate towards split out shared-components module

 * Move shared component source into src/ subdir
 * Fix up imports
 * Include shared components in babel-ing (again)

* Remove now unused dependencies

* Update import in storybook preview

* ...except of course they aren't unused

if we import the shared components by source

* Ignore shared components deps

* Add shared-components to i18n paths

and upgrade web-i18n to version that supports doing so

* Move storybook stuff to shared-components

* Seems we don't need this anymore...

* Remove unused deps

and remove storybook plugin from eslint

* Presumably working-directory is only valid on run steps

* Ignore dep & run prettier

* Prettier on knips.ts

* Hopefully run in right dir

* Remember how to software write

* Okay... how about THIS way?

* Oh right, they were git ignored. Sigh.

* Add concurrently

* Ignore in knip

* Better?

* Paaaaaaaackageeeeeeees

* More packages

* Move playwright snapshots

* Still need a custom snapshots dir

* Add eslint back

* Oh, now knip sees them

* Fix another import

* Don't lint shared-components with everything else

Okay, eslint & tsconfig are tied too closely for this to work and
running tsc on the shared components will need its deps installing

* Maybe lint shared components

please?

* Not quite

* Remove storybook again

Re-check if it does work without it

* Remove storybook eslint plugin

as we're not linting storybook here anymore

* Remove this too

* We do need it here though

webpack.config.js

@@ -265,6 +265,10 @@ module.exports = (env, argv) => {
                         // our own source needs babel-ing
                         if (f.startsWith(path.resolve(__dirname, "src"))) return true;
 
+                        // We import the typescript source directly from shared-components
+                        // to avoid having to build as we dev, so include them too.
+                        if (f.startsWith(path.resolve(__dirname, "packages", "shared-components"))) return true;
+
                         // we use the original source files of js-sdk, so we need to
                         // run them through babel. Because the path tested is the resolved, absolute
                         // path, these could be anywhere thanks to yarn link. We must also not