[Firestore] `where` should use a "type safe" approach

You can currently use any string in the where clause of firestore. When using with converter the fieldPath should be "string safe"

Current implementation:

```ts
where(
fieldPath: string | FieldPath,
opStr: WhereFilterOp,
value: any
): Query;
```

Proposed implementation (when using with converter) :

```ts
where(
fieldPath: Path,
opStr: WhereFilterOp,
value: any
): Query;
```

where Path:

```ts
// Allows dot separated properties of
// for firebase updates
export type UpdatePath =
K extends string
? T[K] extends Record
? T[K] extends ArrayLike
? K | `${K}.${UpdatePath>}`
: K | `${K}.${UpdatePath}`
: K
: never;
export type Path = UpdatePath | keyof T;
```