Add autoReset prop to opt out of automatic form reset on actions

[hassanzadeh-mj]

Closes #29034

React 19 automatically calls form.reset() after every form action completes. This is intentional behavior, but there are legitimate cases where developers need to opt out:

• Multi-step forms where fields shouldn't be cleared between steps
• When a server action fails and the user's input should be preserved
• Forms with manually managed controlled state

This PR adds an autoReset prop to <form> elements. It defaults to true (preserving current behavior), and can be set to false to disable the automatic reset.

Usage

// Default behavior — form resets after action (unchanged)
<form action={myAction}>...</form>

// Opt out of automatic reset
<form action={myAction} autoReset={false}>...</form>