Reuse TypegenConfig for SingleProjectConfigFile

[tobias-tengler]

There are some slight discrepancies between multi- and single-project configs at the moment, with some options only being configurable from multi-project configs, even though the compiler could read and support the same settings from both type of configs (examples: use_import_type_syntax, require_custom_scalar_types, etc.).

Changes

• Flatten TypegenConfig in SingleProjectConfigFile and remove duplicated options
• Inlines no_future_proof_enums from FlowTypegenConfig into TypegenConfig and removes FlowTypegenConfig as it's now no longer required
• When parsing of the config file fails, show the single-project config error first, since that is the configuration most people use

⚠️ Breaking change

This change is a breaking change, as the custom_scalars config option in the single-project config must now be specified as custom_scalar_types.

[facebook-github-bot]

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[facebook-github-bot]

@captbaritone merged this pull request in 4e68155.