feat(content): add fixedSlotPlacement prop (#29233)

Issue number: Internal

---------

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## What is the current behavior?
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Content in the `fixed` slot is always placed after the main content in
the DOM.

## What is the new behavior?
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this PR. -->

- A new `fixedSlotPlacement` prop on Content allows developers to place
fixed content either before or after the main content in the DOM

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

Dev build: `8.0.0-dev.11712072527.1dd97c66`

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screenshots of how the component looks before and after the change. -->

⚠️This feature will not be part of the v8.0 release. As a result, do not
merge this into `feature-8.0`. However, I am putting this PR up based
off `feature-8.0` so it can get reviewed by the team.

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Co-authored-by: Liam DeBeasi <liamdebeasi@users.noreply.github.com>

packages/angular/standalone/src/directives/proxies.ts

@@ -659,7 +659,7 @@ export declare interface IonCol extends Components.IonCol {}
 
 @ProxyCmp({
   defineCustomElementFn: defineIonContent,
-  inputs: ['color', 'forceOverscroll', 'fullscreen', 'scrollEvents', 'scrollX', 'scrollY'],
+  inputs: ['color', 'fixedSlotPlacement', 'forceOverscroll', 'fullscreen', 'scrollEvents', 'scrollX', 'scrollY'],
   methods: ['getScrollElement', 'scrollToTop', 'scrollToBottom', 'scrollByPoint', 'scrollToPoint']
 })
 @Component({
@@ -667,7 +667,7 @@ export declare interface IonCol extends Components.IonCol {}
   changeDetection: ChangeDetectionStrategy.OnPush,
   template: '<ng-content></ng-content>',
   // eslint-disable-next-line @angular-eslint/no-inputs-metadata-property
-  inputs: ['color', 'forceOverscroll', 'fullscreen', 'scrollEvents', 'scrollX', 'scrollY'],
+  inputs: ['color', 'fixedSlotPlacement', 'forceOverscroll', 'fullscreen', 'scrollEvents', 'scrollX', 'scrollY'],
   standalone: true
 })
 export class IonContent {