Allow object expression without overrides

[edgarfgp]

Description

Add support for object expression without overrides.

Before

To create an object expression without overrides, the user has to override a member, even if it is not necessary.

type IFirst = interface end

[<AbstractClass>]
type ClassEnd() = class end

// FS0738 Invalid object expression. Objects without overrides or interfaces should use the expression form 'new Type(args)' without braces.
let objExpr = { new ClassEnd() } 

// Workaround: override a member like ToString, Equals, GetHashCode, etc.
let objExpr = { new ClassEnd() with member this.ToString() = "ClassEnd" }

// Workaround: implement a marker interface
let objExpr = { new ClassEnd() interface IFirst }

type Class() = class end

//FS0738 Invalid object expression. Objects without overrides or interfaces should use the expression form 'new Type(args)' without braces.
let objExpr = { new Class() }

// Workaround: override a member like ToString, Equals, GetHashCode, etc.
let objExpr = { new Class() with member this.ToString() = "ClassEnd" }

// Workaround: implement a marker interface
let objExpr = { new Class() interface IFirst }

After

We won't need to use any workaround to use classes(abstract or non-abstract) in object expressions.

[<AbstractClass>]
type AbstractClass() = class end

// Ok
let objExpr = { new AbstractClass() }

type Class() = class end

// Ok
let objExpr = { new Class() }

• Language suggestion: Allow object expression without overrides fsharp/fslang-suggestions#632
• RFC: (Allow object expression without overrides. fsharp/fslang-design#785)
• RFC discussion: F# RFC FS-632 - Allow object expression without overrides fsharp/fslang-design#781

Checklist

• Test cases added
• Release notes entry updated

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.100.md
LanguageFeatures.fsi	docs/release-notes/.Language/preview.md

[vzarytovskii]

Can be merged after RFC is approved by Don

[psfinaki]

Fabulous work. Thanks for adding tests for the old versions as well. Great stuff Edgar!