config generation: escape map keys with whitespace

[liamcervante]

This PR updates the config generation package so map keys with whitespace are escaped with quotes. This is already handled automatically for the normal attribute generation, and nested blocks are also escaped by default. This PR updates the nested attributes so the keys of nested maps are validated and escaped if necessary. It is only maps that have this problem, attributes in objects cannot contain whitespace and other types (lists, sets, tuples) do not render keys anyway.

The rendering package has this same problem, and so far we've not handled it perfectly but just well enough. We'll continue to do so here, but the code calls out we could modify the HCL library so it exposes the internal functions it uses to detect when escaping is necessary and share those between HCL and Terraform. But so far, we've not had any need to take this too seriously.

Fixes #35752

Target Release

1.9.x

Draft CHANGELOG entry

BUG FIXES

• config generation: escape map keys with whitespaces

[github-actions]

Reminder for the merging maintainer: if this is a user-visible change, please update the changelog on the appropriate release branch.

[apparentlymart]

I guess my experiment over in #34823 would've unintentionally fixed this due to hclwrite already knowing how to properly quote/escape literal strings in the way HCL expects. Maybe I should've pushed a little harder to get the remaining problems with that solved, rather than aborting due the misconception that I wasn't actually fixing anything. 😀

That other (more-ambitious-than-necessary) PR aside, it might be interesting to note that hclwrite's quoting is currently exposed as TokensForValue followed by a call to Tokens.Bytes to get the generated expression source code. Though we already ended up needing to do it for instance keys in package addrs, where all the overhead of hclwrite seemed undesirable, and so we have an inline utility function for HCL-friendly string quoting which you could potentially factor out somewhere so that other code like this could use it.