[IMPROVEMENT] Allow user to control primary/default search sources

[bicole]

Please confirm these before moving forward.

• I have searched for my feature proposal and have not found a work-in-progress/duplicate/resolved/discarded issue.
• This improvement refers to an existing feature. If you want to suggest a new feature, please use this template.
• This improvement is not a bug. If you want to report a bug, please use this template.

Describe the improvement

Allow the user to select or specify which of the package manager sources they wish to use during searches instead of searching all of them at once.

Suggestions for search improvements:

• Provide an option per package manager to include in every search (even though it can be toggled off during each search instance)
• Provide a search settings page section to select which sources should be searched first and then how/when to start searches for other sources
• Allow the user to control which package manager is used for a search in the search bar api or keywords.
  • Example: to search for package in only the winget package manager.
    • "pm:winget <package>" or "winget:<package>"
  • Example: to search winget and scoop and any other comma-separated package manager for the package provided.
    • "pm:winget,scoop,... <package>"
• Allow the user to dynamically change the default/preferred list of sources in the search results window.

Describe how this improvement could help users

This would help users to in terms of performance hit when searching if multiple package managers are enabled due to the search feature automatically searching all sources instead of a select few upon request.