[Focus]: Set delegatesFocus on all components

[fallaciousreasoning]

This delegates the focus to the first focusable element (or the element with autofocus) inside the shadowDOM when .focus() is called on the element.

I don't know if we want this for every component, but it does seem like a sensible default.

https://developer.mozilla.org/en-US/docs/Web/API/ShadowRoot/delegatesFocus

[fallaciousreasoning]

@petemill @AlanBreck any idea of the wider implications of this?

[github-actions]

👋 Thanks for Submitting! This PR is available for preview at the link below.

✅ PR tip preview: https://559.pr.nala.bravesoftware.com/
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Variables Diff

--- ./tokens/css/variables.old.css	2024-02-20 22:26:26.141932107 +0000
+++ ./tokens/css/variables.css	2024-02-20 22:25:59.294033083 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Tue Feb 20 2024 20:43:18 GMT+0000 (Coordinated Universal Time)
+ * Generated on Tue Feb 20 2024 22:25:59 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

[AlanBreck]

which may be undesirable if that element is not meant to be part of the tabbing order (for example, an element with tabindex="-1"), or if a more 'important' focusable element should receive initial focus (for instance, the first text field rather than the 'close' button which precedes it).

This seems like a caveat worth consideration. What are the negatives of not doing this?

[fallaciousreasoning]

The negatives of not doing this are that for elements like the Button, Input, Dropdown ect calling .focus() on the HTMLElement doesn't behave as expected.

However, it sounds like we might not want this for non input type="..." components? I dunno.

WICG/webcomponents#126 (comment)

[fallaciousreasoning]

FWIW, @nullhook PR brave/brave-core#22220 depends on this.

Maybe we need to come up with a way for components to opt in/out of this behavior?

[fallaciousreasoning]

Going to not merge this for another couple of days, for the brave-core release