feat: slug field (#14007)

Discussion #8859. Requires #14012.

Exports a new `slugField`. This is a wrapper around the text field that
you can drop into any field schema.

A slug is a unique, indexed, URL-friendly string that identifies a
particular document, often used to construct the URL of a webpage. Slugs
are a fundamental concept for seemingly every project.

Traditionally, you'd build this field from scratch, but there are many
edge cases and nice-to-haves to makes this difficult to maintain by
hand. For example, it needs to automatically generate based on the value
of another field, provide UI to lock and re-generate the slug on-demand,
etc.

Fixes #13938.

When autosave is enabled, the slug is only ever generated once after the
initial create, leading to single character, or incomplete slugs.

For example, it is expected that "My Title" → "my-title, however ends up
as "m".

This PR overhauls the field to feel a lot more natural. Now, we only
generate the slug through:
1. The `create` operation, unless the user has modified the slug
manually
2. The `update` operation, if:
  a. Autosave is _not_ enabled and there is no slug
b. Autosave _is_ enabled, the doc is unpublished, and the user has not
modified the slug manually

The slug should stabilize after all above criteria have been met,
because the URL is typically derived from the slug. This is to protect
modifying potentially live URLs, breaking links, etc. without explicit
intent.

This fix, along with all the other features, is now standardized behind
the new `slugField`:

```ts
import type { CollectionConfig } from 'payload'
import { slugField } from 'payload'

export const MyCollection: CollectionConfig = {
  // ...
  fields: [
   // ...
   slugField()
  ]
}
```

In the future we could also make this field smart enough to auto
increment itself when its generated slug is not unique.

---
- To see the specific tasks where the Asana app for GitHub is being
used, see below:
  - https://app.asana.com/0/0/1211513433305005

Author: jacobsfletch

docs/fields/collapsible.mdx

@@ -66,8 +66,6 @@ The Collapsible Field inherits all of the default admin options from the base [F
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/date.mdx

@@ -96,8 +96,6 @@ When only `pickerAppearance` is set, an equivalent format will be rendered in th
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/email.mdx

@@ -74,8 +74,6 @@ The Email Field inherits all of the default admin options from the base [Field A
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/group.mdx

@@ -77,8 +77,6 @@ The Group Field inherits all of the default admin options from the base [Field A
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/json.mdx

@@ -75,8 +75,6 @@ The JSON Field inherits all of the default admin options from the base [Field Ad
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/number.mdx

@@ -80,8 +80,6 @@ The Number Field inherits all of the default admin options from the base [Field
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/point.mdx

@@ -55,8 +55,6 @@ _\* An asterisk denotes that a property is required._
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/radio.mdx

@@ -90,8 +90,6 @@ The Radio Field inherits all of the default admin options from the base [Field A
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/row.mdx

@@ -43,8 +43,6 @@ _\* An asterisk denotes that a property is required._
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'
 

docs/fields/select.mdx

@@ -149,8 +149,6 @@ The Select Field inherits all of the default admin options from the base [Field
 
 ## Example
 
-`collections/ExampleCollection.ts`
-
 ```ts
 import type { CollectionConfig } from 'payload'