Increase strictness of `tsconfig`

### Is your feature request related to a problem? Please describe.

Currently `tsconfig.base.json` has quite low strictness, and Typescript is not helping the developer as much as it could.

Also, there is a higher change of bugs arising without this strictness.

I suggest `"strict": true` and `"noUncheckedIndexedAccess": true` is added to `tsconfig`, but there are also some other settings that could be interesting.

Matt Pocock has a good blog post here: [https://www.totaltypescript.com/tsconfig-cheat-sheet](https://www.totaltypescript.com/tsconfig-cheat-sheet).

In case this is something that could be added, we should start by updating `@jsonforms/core` and could afterwards do other packages.

It would require quite a bit of (small) changes several places.

### Describe the solution you'd like

`packages/core/tsconfig.json`:
```jsonc
{
"compilerOptions": {
"verbatimModuleSyntax": true,
/* strictness */
"strict": true,
"noUncheckedIndexedAccess": true,
}
}
```

see also:
- [strict](https://www.typescriptlang.org/tsconfig#strict)
- [noUncheckedIndexedAccess](https://www.typescriptlang.org/tsconfig#noUncheckedIndexedAccess)

### Describe alternatives you've considered

.

### Framework

Core

### RendererSet

_No response_

### Additional context

_No response_

Beginne mit dem Lesen von tsconfig.base.json und packages/core/tsconfig.json und konzentriere dich dabei auf die vorgeschlagenen Strictness-Optionen für @jsonforms/core. Überprüfe die TypeScript-Fehler, die nach dem Aktivieren von strict und noUncheckedIndexedAccess erzeugt werden, und nimm anschließend die erforderlichen kleinen Änderungen im gesamten Paket vor. Als erledigt gilt die Aufgabe, wenn das Core-Paket mit beiden aktivierten Optionen fehlerfrei erstellt wird.

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