Provide better story for individual migration results

This issue impacts 9.0.0-rc.0 and happened while updating https://github.com/johannesjo/super-productivity and https://github.com/SAP/cloud-commerce-spartacus-storefront.

A failed update will show a message saying both the individual migration and the update failed:
```
× Package install failed, see above.
The update failed. See above.
git HEAD was at 85f08a4d93e684566f751e38e2a2feffe0194cd9 before migrations.
× Migration failed. See above for further details.
```

The update below did not finish successfully however, and instead just shows the last migration as successful (@devversion confirms this). In this case the migration shows an error that it seems to suggest was actually recovered from, but it fact the intent is that the migration was interrupted and should later be resumed.
```
> Undecorated classes with DI migration.
As of Angular 9, it is no longer supported to use Angular DI on a class that does not have an Angular decorator.
Read more about this here: https://v9.angular.io/guide/migration-undecorated-classes

This migration uses the Angular compiler internally and therefore projects that no longer build successfully after the update cannot run the migration. Please ensure there are
no AOT compilation errors and rerun the migration.. The following project failed: projects/storefrontlib/tsconfig.lib.json

TypeError: Cannot read property 'module' of undefined

Could not migrate all undecorated classes that use dependency
injection. Some project targets could not be analyzed due to
TypeScript program failures.

Migration can be rerun with: "ng update @angular/core --from 8.0.0 --to 9.0.0 --migrate-only"

√ Migration succeeded.
```

A completely successful migration will look the same as the migration above though:
```
kamik@RED-X1C6 MINGW64 /d/sandbox/latest-app (master)
$ ng update @angular/cli @angular/core --next
The installed Angular CLI version is older than the latest published version.
Installing a temporary version to perform the update.
Installing packages for tooling via yarn.
warning @angular-devkit/architect@0.900.0-rc.0: The engine "pnpm" appears to be invalid.
warning @schematics/angular@9.0.0-rc.0: The engine "pnpm" appears to be invalid.
warning @angular-devkit/schematics@9.0.0-rc.0: The engine "pnpm" appears to be invalid.
warning @angular-devkit/core@9.0.0-rc.0: The engine "pnpm" appears to be invalid.
warning @schematics/update@0.900.0-rc.0: The engine "pnpm" appears to be invalid.
warning @angular/cli@9.0.0-rc.0: The engine "pnpm" appears to be invalid.
Installed packages for tooling via yarn.
Using package manager: 'yarn'
Collecting installed dependencies...
Found 35 dependencies.
Fetching dependency metadata from registry...
Updating package.json with dependency @angular/cli @ "9.0.0-rc.0" (was "8.3.17")...
Updating package.json with dependency @angular/core @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/language-service @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/compiler-cli @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/animations @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/platform-browser @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/platform-browser-dynamic @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/common @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/compiler @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/forms @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular/router @ "9.0.0-rc.0" (was "8.2.13")...
Updating package.json with dependency @angular-devkit/build-angular @ "0.900.0-rc.0" (was "0.803.17")...
UPDATE package.json (1636 bytes)
√ Packages installed successfully.
** Executing migrations of package '@angular/cli' **

> Update an Angular CLI project to version 9.
UPDATE angular.json (6359 bytes)
UPDATE package.json (1637 bytes)
UPDATE server.ts (1863 bytes)
√ Packages installed successfully.
√ Migration succeeded.

> Update lazy loading syntax to use dynamic imports.
√ Migration succeeded.

** Executing migrations of package '@angular/core' **

> Static flag migration.
Removes the `static` flag from dynamic queries.
As of Angular 9, the "static" flag defaults to false and is no longer required for your view and content queries.
Read more about this here: https://v9.angular.io/guide/migration-dynamic-flag
√ Migration succeeded.

> Missing @Injectable migration.
In Angular 9, enforcement of @Injectable decorators for DI is a bit stricter.
Read more about this here: https://v9.angular.io/guide/migration-injectable
√ Migration succeeded.

> ModuleWithProviders migration.
In Angular 9, the ModuleWithProviders type without a generic has been deprecated.
This migration adds the generic where it is missing.
Read more about this here: https://v9.angular.io/guide/migration-module-with-providers
√ Migration succeeded.

> NGCC postinstall migration.
Adds an ngcc invocation to npm/yarn's postinstall script.
Read more about this here: https://v9.angular.io/guide/migration-ngcc
UPDATE package.json (1743 bytes)
√ Packages installed successfully.
√ Migration succeeded.

> Renderer to Renderer2 migration.
As of Angular 9, the Renderer class is no longer available.
Renderer2 should be used instead.
Read more about this here: https://v9.angular.io/guide/migration-renderer
√ Migration succeeded.

> Undecorated classes with decorated fields migration.
As of Angular 9, it is no longer supported to have Angular field decorators on a class that does not have an Angular decorator.
Read more about this here: https://v9.angular.io/guide/migration-undecorated-classes
√ Migration succeeded.

> Undecorated classes with DI migration.
As of Angular 9, it is no longer supported to use Angular DI on a class that does not have an Angular decorator.
Read more about this here: https://v9.angular.io/guide/migration-undecorated-classes
√ Migration succeeded.
```

We should confirm the update finished, was successful, or if it was interrupted midway and should later be continued.

Beginne damit, die gemeldete Ausgabe über den Einstiegspunkt `ng update` zu reproduzieren, und verwende dabei die im Issue enthaltenen Beispiele für fehlgeschlagene und erfolgreiche Migrationen. Verfolge, wie einzelne Migrationen Ergebnisse melden, und sorge dafür, dass die endgültige Ausgabe ein abgeschlossenes Update von einem unterbrochenen Update unterscheidet, das fortgesetzt werden sollte; überprüfe, dass beide Szenarien genaue Statusmeldungen erzeugen.

Vom Indexierungsmodell aus dem Issue-Text verfasst.