[iOS] Create a cache system for images

[mltokky]

Issue

• close [iOS] Create a cache system for images #430

Overview (Required)

• create view for user icon
  • The view use in in-memory cache if speaker icon data exists in it, else fetched from server.
  • URLSession may returns data from cache after second time, so speaker icon is displayed faster than before.

Movie (Optional)

launch at first time

Before	After
430_before.mp4	430_after.mp4

launch at second time

Before	After
---	430_2_after.mp4

[shin-usu]

@mltokky
Thank you for your commit! Great!!
SpeakerIcon component could be applied to other screens.
If you have time, could you please apply it to the following screens as well?

• TimetableDetailView
• ContributorListItemView
• StaffView

Of course, you can refuse.
This commitment is enough to resolve the issue.

[mltokky]

@shin-usu
Sorry for the late reply.

Yes, I'll apply it!
May I continue on this PR?

[shin-usu]

@shin-usu
Yes! Thank you very much🙇‍♂️

[mltokky]

@shin-usu
Applying to other screens is done!
Please review changed code.

Notes

• I renamed component to CircularUserIcon from SpeakerIcon because it is no longer just about displaying speaker icon.
• I found app crash in Staff screen, Contributor -> KMP Presenter, and KMP Compose view. So I could not confirm these screens.

[shin-usu]

Thank you very much😊
I'll check the pull request later.

About crashes, this bug is known issue.
#527

It is sufficient to check only SwiftUI view on ContributorView👍

[shin-usu]

I think it would be appropriate to rename this actor as well as circular icon view.
What do you think?

[mltokky]

Oh, sorry...
I forgot rename this actor.

I fixed it.
Please check again 🙏🏻

[shin-usu]

LGTM🎉 Thank you for your commitment to my additional request!