[form] Add actionsRef

[mj12albert]

Form:

const actionsRef = React.useRef<Form.Actions>(null);

<Form actionsRef={actionsRef} />>

// validate all fields
actionsRef.current?.validate();
// validate one field by name
actionsRef.current?.validate('username');

Field:

const actionsRef = React.useRef<Field.Root.Actions>(null);

<Field.Root actionsRef={actionsRef} />>

// validate the field
actionsRef.current?.validate();

Closes #3323

• I have followed (at least) the PR section of the contributing guide.

[pkg-pr-new]

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui-components/react@3395
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui-components/utils@3395
  

commit: 40c2427

[mui-bot]

Bundle size report

Bundle	Parsed size	Gzip size
@base-ui-components/react	🔺+366B(+0.09%)	🔺+105B(+0.08%)

Details of bundle changes

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