Backport of update github.com/zclconf/go-cty@v1.9.1 into v1.0

[ghost]

Backport

This PR is auto-generated from #29406 to be assessed for backporting due to the inclusion of the label 1.0-backport.

The below text is copied from the body of the original PR.

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• cty: Don't panic in Value.Equals if comparing complex data structures with nested marked values. Instead, Equals will aggregate all of the marks on the resulting boolean value as we typically expect for operations that derived from marked values. (#112)
• cty: Value.AsBigFloat now properly isolates its result from the internal state of the associated value. It previously attempted to do this (so that modifying the result would not affect the supposedly-immutable cty.Number value) but ended up creating an object which still had some shared buffers. The result is now entirely separate from the internal state of the recieving value. (#114)
• function/stdlib: The FormatList function will now return an unknown value if any of the arguments have an unknown type, because in that case it can't tell whether that value will ultimately become a string or a list of strings, and thus it can't predict how many elements the result will have. (#115)

Fixes #29339
Fixes #29301

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