feat(CdkMenu): Option to disable typeahead in CdkMenu

[twittwer]

Feature Description

We would like to add an option in the CdkMenu to disable the integrated TypeAhead feature.

Currently, the menu activates the TypeAhead for its FocusKeyManager automatically:

components/src/cdk/menu/menu-base.ts

Line 175 in e91d509

this.keyManager = new FocusKeyManager(this.items).withWrap().withTypeAhead().withHomeAndEnd();

The proposal would be to add an input like cdkMenuTypeAhead: boolean which defaults to true but can be used to skip the TypeAhead activation:

this.keyManager = new FocusKeyManager(this.items).withWrap().withHomeAndEnd();
if (this.cdkMenuTypeAhead) {
  this.keyManager = this.keyManager.withTypeAhead()
}

Alternative

An alternative approach might be a combination of the following features, so the described use case can be accomplished by the CdkMenu itself.

1. Make the current search term (_pressedLetters) publicly available, so it can be displayed.
2. Two variants to extend the current search logic:
   2.a Add a secondary includes search to the current startsWith.
   2.b Make the search logic customizable with configurable predicate function.

Use Case

The use case is a custom search feature for our menus, which conflicts with the integrated TypeAhead.
We want to display the current search term and search by startsWith & includes.

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🗨 I would appreciate some feedback, if this feature has a chance of being accepted. Then I can prepare a PR for this.

[wagnermaciel]

A not great but easy workaround would be to define a typeaheadLabel that's some non-typeable character

<button cdkMenuitemTypeaheadLabel="👍" cdkMenuItem>Inbox</button>