[lexical] Chore: Add more helpful invariants to $applyNodeReplacement

[etrepum]

Description

Specifying the key argument incorrectly in a replacement function is a common mistake. This PR adds a helpful invariant and improves the error messages in the existing invariants for $applyNodeReplacement.

Test plan

Before

It was possible to write code that behaves incorrectly in subtle ways without a clear error message if you wrote a replacement function that preserved a node's __key incorrectly, e.g. https://discord.com/channels/953974421008293909/1278046226100654243

After

Invariants will throw an error early if this type of mistake is made with enough information to fix it.

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Name	Status	Preview	Comments	Updated (UTC)
lexical	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 10, 2024 2:22pm
lexical-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 10, 2024 2:22pm

[github-actions]

size-limit report 📦

Path	Size
lexical - cjs	29.61 KB (0%)
lexical - esm	29.49 KB (0%)
@lexical/rich-text - cjs	38.14 KB (0%)
@lexical/rich-text - esm	31.3 KB (0%)
@lexical/plain-text - cjs	36.71 KB (0%)
@lexical/plain-text - esm	28.65 KB (0%)
@lexical/react - cjs	39.85 KB (0%)
@lexical/react - esm	32.79 KB (0%)