Insert mode `<C-m>` and `<C-j>` should behave the same as the Enter key

Is your feature request related to a problem? Please describe.
In vim insert mode <C-m> is the exact same as Enter / <CR>. In VSCodeVim it just inserts a newline character.
This is an issue because it does not indent the next line if it needs indentation. Some extensions also run functionality on the Enter key.

Another problem because of this is you can't use <C-m> to select suggestions / auto-completion like you can in vim (#5497).

Describe the solution you'd like
Make it the same as the Enter key.

Describe alternatives you've considered

Adding a keybinding with the command editor.action.insertLineAfter, but if you use in the middle of the line, it doesn't work as desired.

Using vim.insertModeKeyBindingsNonRecursive works:

{
    "vim.insertModeKeyBindingsNonRecursive": [
        {
            "before": ["<C-m>"],
            "after": ["<Enter>"]
        }
    ],
}

But it should be default behavior.

Start by tracing the VSCodeVim insert-mode key handling for Ctrl-M, Ctrl-J, and Enter. Compare their behavior for line breaks, indentation, and completion selection, then add or update focused tests if the relevant test entry point is found. Done means both control keys behave like Enter in insert mode, including in the middle of a line.