Consider adding shallow clone support to ToolSettings

[augustoproiete]

Tracking suggestion by @mholo65 and @patriksvensson on discussion related to #3044

Goal: Define default values for tool settings. For example, MSBuildSettings: set a number of values, and use that as a default when calling MSBuild.

Pseudo-code of possible usage:

var msbuildDefaultSettings = new MSBuildSettings
{
    // By default, we want to use MSBuild VS2017 on all tasks
    ToolVersion = MSBuildToolVersion.VS2017,

    // ... (set other defaults)
};

Task("A")
    .Does(_ =>
{
    var msbuildSettings = msbuildDefaultSettings.Clone();

    msbuildSettings.Configuration = "Debug";
    // ... (override other properties of msbuildSettings as needed)

    MSBuild("./MyConsoleApp/MyConsoleApp.csproj", msbuildSettings);
});

Task("B")
    .Does(_ =>
{
    var msbuildSettings = msbuildDefaultSettings.Clone();

    msbuildSettings.Configuration = "Release";
    // ... (override other properties of msbuildSettings as needed)

    MSBuild("./MyConsoleApp/MyConsoleApp.csproj", msbuildSettings);
});

// ...

[augustoproiete]

Relates to #2103. This is about adding clone support to the base class ToolSettings whereas #2103 is about adding clone specifically to MSBuildSettings