chore: update Angular to v21

[michael-small]

Note: this PR is about getting all of our dependencies inline with Angular v21, but this is not about releasing the toolkit's v21. We have a few things after merging this in that we are preparing before a toolkit v21.

Compared to closed previous PR, worked fine the first time.

Notes @rainerhahnekamp

1. Pointing at NgRx release candidate at the moment now v21 stable
2. This is not currently specifying the toolkits package's version, in case there is some CI tooling that may pick up on a change and maybe we want to merge this then tweak stuff later. Like if we want to merge this today then bump NgRx when 21 stable is out.
3. The NgRx deps are not just a package.json change, but also the lib's package.json needs to specify the correct version of them to target as well. also points at v21 stable

[SerkanSipahi]

@rainerhahnekamp do you plan to deploy this on npm?

[rainerhahnekamp]

@SerkanSipahi, yes, but we want to have first the merge for events tracking (#233) and the fix for withResource (#242).

Probably after Christmas but before the New Year

[SerkanSipahi]

@michael-small thanks for the clarification. I wish you and your family a merry Christmas. See you next year. Since I have no more holiday left for this year, I am still working hard.