--update-project feature work

[deepchoudhery]

Draft PR for now.

Will have more incoming changes and tests throughout the review.
Code changes are done through json configs. Only C# files are edited.

Each project type/scenario should have a json config file for itself.

class CodeModifierConfig
{
    public string? Identifier { get; set; } --> identifier for project type/scenario.
    public File[]? Files { get; set; } --> All the files that need editing in the project.
}

class File
{
    public Dictionary<string, Method>? Methods { get; set; } --> all the methods in the file that need editing
    public string[]? Usings { get; set; } --> any `usings` that need to be added to a C# file. 
    public string? FileName { get; set; } --> .cs file to edit
    public string[]? ClassProperties { get; set; } --> any properties that need to be added to the class' members.
    public string[]? ClassAttributes { get; set; } --> [Attribute] that need to added to the class.
}

class Method
{
    public string[]? Parameters { get; set; } --> parameter types for the method. Used to get the correct ParameterSyntax.
    public CodeChange[]? CodeChanges { get; set; } --> All the changes within a particular method.
}
class CodeChange
{
    public string? InsertAfter { get; set; } --> Insert new statement block after this statement syntax node.
    public string? Block { get; set; } --> C# statement that is parsed using SyntaxFactory.ParseStatement
    public string? Parent { get; set; } --> Add C# statement syntax node upon this parent statement syntax node based on Type 
    public string? Type { get; set; } --> CodeChangeType (below) string.
    public bool? Append { get; set; } = false; --> Insert Block at the top of the method.
}

class CodeChangeType
{
    public const string MemberAccess = nameof(MemberAccess); --> Add a SimpleMemberAccess expression to the parent statement syntax. 
    public const string InLambdaBlock = nameof(InBlock); --> Add in lambda block to the parent statement syntax. 
}

This info is also available in CodeModifierConfig folder as well.

The scenarios below need to be supported for all project types :

Scenario	Status
ASP .NET Core Web App	Config w/out layout(.cshtml) files
ASP .NET Core Web App (w/ B2C tenant)	Config w/out layout(.cshtml) files
ASP .NET Core Web Api	Config w/out layout(.cshtml) files
ASP .NET Core Web Api (w/ B2C tenant)	Config w/out layout(.cshtml) files
Blazor Server App	Need config
Blazor Server App (w/ B2C tenant)	Need config
Blazor WebAssembly App	Need config
Blazor WebAssembly App (w/ B2C tenant)	Need config
Blazor Hosted WebAssembly App	Need config
Blazor Hosted WebAssembly App (w/ B2C tenant)	Need config

[abpiskunov]

    private static void SetUserSecerets(string projectPath, string key, string value, IConsoleLogger consoleLogger)

nit: Secrets

---

Refers to: src/MSIdentityScaffolding/Microsoft.DotNet.MSIdentity/CodeReaderWriter/CodeWriter.cs:150 in 9a50b7f. [](commit_id = 9a50b7f, deletion_comment = False)

[deepchoudhery]

Carrying over comments from https://github.com/dotnet/Scaffolding/pull/1582/files/7435445dfe7c11b8e1f872a83dd1777b0a1f7dae

[deepchoudhery]

Review carried over from #1582

[abpiskunov]