Update `code_suggestions_in_web_ide_spec` to enter the prompt more like a user

What does this MR do and why?

Updates the e2e test qa/specs/features/ee/browser_ui/3_create/web_ide/code_suggestions_in_web_ide_spec.rb to enter the code suggestions prompt more like a user would.

• Waits for the status icon to show that code suggestions is enabled before entering the prompt

• Enters the prompt to one key at a time to allow the suggestion to be triggered successfully

• Waits for 60 seconds for the suggestion to appear. Code generation could take longer than 30 seconds sometimes (not likely, but this should avoid that possible source of flakiness)

• After this is merged the test should be removed from fast quarantine.

Screenshots or screen recordings

Here's the test running against Staging:

web_ide_code_suggestions

Background

• The test failure triggered an incident: gitlab-com/gl-infra/production#17253 (closed)
• The cause was related to the code_generation_anthropic feature flag. It needed to be enabled to allow the WebIDE to return suggestions as code generation after code-bison (via Vertex) was no longer used: #434867 (comment 1689333542). The flag is now enabled for gitlab-qa.
• There was still some flakiness after enabling the feature flag, hence this MR. See #434867 (comment 1689631415)

How to set up and validate locally

To run the test against Staging, the following from the qa directory:

export GITLAB_USERNAME=gitlab-qa 
export GITLAB_PASSWORD=<from 1Password> 
export GITLAB_QA_ACCESS_TOKEN=<from 1Password> 
export GITLAB_QA_USER_AGENT=<from 1Password> 
bundle install
bundle exec bin/qa Test::Instance::All https://staging.gitlab.com qa/specs/features/ee/browser_ui/3_create/web_ide/code_suggestions_in_web_ide_spec.rb

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 #434867 (closed)