feat(store): split Immutable checks in state and action checks

[timdeschryver]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Closes #1890

What is the new behavior?

Does this PR introduce a breaking change?

A breaking change for v8 beta

[x] Yes
[ ] No

runtimeChecks: {
-  strictImmutability: true,
+  strictStateImmutability: true,
+  strictActionImmutability: true,
   strictStateSerializability: true,
   strictActionSerializability: true,
},