cargo-upgrade and single item tables

[Tosainu]

cargo upgrade collapses a table if it has only one item and produces the line without a space after the crate name.

[dependencies]
inline_table = { version = "0.1.0" }
string = "0.1.0"

[dependencies.table]
version = "0.1.0"

[dependencies]
inline_table = "0.1.0"
string = "0.1.0"
table= "0.1.0"

This PR changes to preserve a single item table to avoid this problem.

Fixes #717

[epage]

Could you open an issue for this? I'd like to discuss the problem statement and how we plan to solve that and prefer that to be in issues and leaving PRs for the implementation. For example, sometimes there ends up being multiple PR attempts for the same issue and having the common info all in one place is helpful

[Tosainu]

➡️ #717

[epage]

Superseded by #725