Add FilterOptions for get available package summaries.

[absoludity]

Description of the change

Adds an initial FilterOptions message to the GetAvailablePackageSummariesRequest
able to handle existing filter options for direct helm..

Benefits

We can handle filter options for existing helm implementation.

Applicable issues

• Ref [kubeapps-apis] Implement "direct-Helm" plugin based on the existing features in kubeapps #2993

Additional Information

Looks like someone's editor is leaving trailing blank spaces - they're being cleaned up when I save a proto file, but it causes the generation to differ etc. Might be worth checking.

[antgamdia]

Thanks for adding this msg!
I didn't notice the formatting issues, have you used any automatic linter?

[absoludity]

Thanks for adding this msg!
I didn't notice the formatting issues, have you used any automatic linter?

Just

    "files.insertFinalNewline": true,
    "files.trimTrailingWhitespace": true,

in my VSCode settings.