fix(combo/simple-combo): prevent Escape from closing parent container on clear - master

[georgianastasov]

Closes #17119

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them

[Copilot]

Pull request overview

Fixes an issue where pressing Escape inside igx-combo / igx-simple-combo (e.g., to clear or close the dropdown) was also bubbling up and closing a parent container like igx-dialog (overlay closeOnEscape).

Changes:

• Stop Escape keydown event propagation in IgxComboComponent and IgxSimpleComboComponent.
• Add unit tests asserting stopPropagation() is invoked for Escape handling.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
projects/igniteui-angular/simple-combo/src/simple-combo/simple-combo.component.ts	Stops Escape keydown bubbling during SimpleCombo key handling to avoid parent overlay/dialog close.
projects/igniteui-angular/simple-combo/src/simple-combo/simple-combo.component.spec.ts	Adds tests verifying Escape keydown calls stopPropagation() in relevant SimpleCombo states.
projects/igniteui-angular/combo/src/combo/combo.component.ts	Stops Escape keydown bubbling in Combo HostListener handler to prevent parent overlay/dialog close.
projects/igniteui-angular/combo/src/combo/combo.component.spec.ts	Adds tests verifying Escape keydown calls stopPropagation() in relevant Combo states.