Add support to search by iid in work item input component

What does this MR do and why?

This MR covers following parts of Add support of pasting links and search by refe... (#427594 - closed)

• Add support of search by reference ids
• Highlight items like in global search

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
Screen Recording 2023-10-27 at 5.16.36 PM.mov	Screen Recording 2023-10-27 at 5.15.23 PM.mov

How to set up and validate locally

Prerequisites:

1. Enable the OKRs feature as mentioned in the OKRs docs (e.g. ::Feature.enabled?(:okrs_mvc, Project.find(<PROJECT_ID>)) and the namespace must have Ultimate plan).
2. Enable the feature flag Feature.enable(:linked_work_items)

Steps to verify:

1. Login with any user
2. Go to any Project > Issues > List
3. Create an new Objective under New issue split button
4. Go to Objective detail page
5. Under Linked Items, click on Add button to open the form
6. Use different search terms to validate
   1. If there is only a number, it should start searching by iid and numbers in the text
   2. If it is search input is text or space is added, it should search by text
7. It should highlight the searched term like in global search

This also affects the Child objectives and key results widget above Linked Items . Try to search and add any Objective/Key result using Add > Existing objective/key result option in the Child objectives and key results widget.

Moreover, for Tasks in issues. Search and Add a Task as mention Add a Task docs under an Issue

Limitations:

• There is no partial search when searched by iid as currently it is not supported in the GraphQL query.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #427594 (closed)