Migrate `toml` to be on `toml_edit`

[epage]

toml will be a wrapper around the toml_edit crate, providing serde integration, decoupled from the format-preserving parsing, and offering a more stable API

As part of switching cargo adopting toml_edit, toml_edit::easy, a copy of tomls API, was created so cargo could have a single toml parser for both serde and editing.

We plan to move toml_edit::easy into the toml crate, providing nearly the same API at nearly the same performance while reducing overall maintenance effort and allowing people who have both needs to have a common parser.

Blockers

• toml_edit is pretty slow to compile #327
• Support semantic error messages by supporting deserializing spans #302
• Support reporting line/column in serialization errors #303
• Release a 0.5 with deprecations and 1.48 MSRV (MSRV policy #346)
  • Deserializer::end
  • Deserializer::set_require_newline_after_table
  • Deserializer::set_allow_duplicate_after_longer_table

Performance

• See Port cargo from toml-rs to toml_edit rust-lang/cargo#10086 (comment)

Compatibility

• Rendering of strings doesn't match toml-rs #287
• fix(toml): Deprecate compat hacks #344