[Table] adds rowSpacing property

[nero-angela]

Description

Adds a rowSpacing property to the Table class.

before add rowSpacing	after add rowSpacing="10"

Related Issues

Fixes #52248

Tests

I added the following tests:

• Tests to ensure that additional space is added in between each TableRow.

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Breaking Change

Did any tests fail when you ran them? Please read Handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.

[Piinks]

This kind of reminds me of #16957, which was decided not to be added to the framework.
I could see how supporting row spacing would logically call on support for Column spacing as well.
If we follow the recommendation in the Row/Column spacing discussion in #16957, maybe adding an empty TableRow in between the other TableRows is a better approach? Not sure.

[nero-angela]

@Piinks Unlike Row / Column, Table can only receive TableRow as a child, and each TableRow must have the same number of columns. So I can add space like the below code.

TableRow(
  children: <Widget>[
    Container(child: Text('1'), height: 100),
    Container(child: Text('2'), height: 100),
    Container(child: Text('3'), height: 100),
  ],
),
TableRow(
  children: <Widget>[
    SizedBox(height: 10),
    SizedBox(height: 10),
    SizedBox(height: 10),
  ],
),
TableRow(
  children: <Widget>[
    Container(child: Text('4'), height: 100),
    Container(child: Text('5'), height: 100),
    Container(child: Text('6'), height: 100),
  ],
),

There may be other ways I don't know, Wrap cannot be used and SizedBox or Padding corresponding to the number of columns must be implemented.

And I think we should compare the Table with the GridView, not the Row/Column.
In the GridView, there are crossAxisSpacing and mainAxisSpacing properties. In fact, these properties can also be implemented a variety of ways.

In addition, the Table is less complex than the Row/Column. So I think it's okay to add rowSpacing to Table, But If you don't agree with it, I would close this PR.

For reference, in the widget of the week introduces the Table like the below.

If you have a grid of widgets that you don't want to scroll?
That's what Table is for!

[goderbauer]

I am also not convinced that adding this is a good idea. If we'd do this, we'd probably also have to provide a way to add padding between the cells in one row. Just having rowPadding seems odd. It's also not terribly difficult to get this spacing without extra framework support:

          TableRow spacer = TableRow(
            children: <Widget>[
              SizedBox(height: 10),
              SizedBox(height: 10),
              SizedBox(height: 10),
            ],
          );

          Table(
            children: [
              TableRow(
                children: <Widget>[
                  Container(child: Text('1'), height: 100),
                  Container(child: Text('2'), height: 100),
                  Container(child: Text('3'), height: 100),
                ],
              ),
              spacer,
              TableRow(
                children: <Widget>[
                  Container(child: Text('4'), height: 100),
                  Container(child: Text('5'), height: 100),
                  Container(child: Text('6'), height: 100),
                ],
              ),
              spacer,
              TableRow(
                children: <Widget>[
                  Container(child: Text('7'), height: 100),
                  Container(child: Text('8'), height: 100),
                  Container(child: Text('9'), height: 100),
                ],
              ),
            ],
          ),

[goderbauer]

Presumably, this also needs changes to the intrinsics methods.

[nero-angela]

If adding rowSpacing isn't a good idea, it might be better to close this PR and the related issue. 🙏