User and account forms set no autocomplete attributes

[bpmore]

Bug description

The user create and account forms collect a person's own name and email but set no autocomplete attribute, so browsers and assistive technology cannot identify the fields for autofill.

Measured on /cp/users/create:

name   type=text   autocomplete: null
email  type=email  autocomplete: null

The login form already does this correctly, which is what makes the omission look accidental rather than deliberate:

email     autocomplete="username"
password  autocomplete="current-password"

WCAG 2.1 SC 1.3.5 Identify Input Purpose (Level AA).

How to reproduce

1. composer create-project statamic/statamic, log in
2. Visit /cp/users/create (or /cp/account)
3. In the console:

[...document.querySelectorAll('input')].map(i => [i.name || i.id, i.getAttribute('autocomplete')])

Every value is null.

Suggested fix

Two parts, and the second is the more useful one:

1. Set autocomplete="name" and autocomplete="email" on the name and email fields in the user blueprint.
2. Expose an autocomplete config key on the Text fieldtype so blueprint authors can satisfy 1.3.5 on their own front-end and CP forms. Right now there is no way to set it from a blueprint at all, which means any Statamic site collecting a user's own details in a CP form inherits this.

Filing rather than PRing because (2) is an API addition and the config key naming is yours to choose. Happy to implement whichever shape you'd prefer.