Don't show tons of artist external links in tooltip by default

[towerofnix]

Back in the day the limit (once we put one in place) was four. We can probably go one or two higher than this, and implement a "Show 6 more links..." action.

We should try to be reasonably smart about which external links we display (instead of just selecting the first N links). A linktree or similar site is probably always useful to show at the bottom. An artist may have multiple SoundCloud links in sequence in their uRLs - we may wish to prioritize links of different platforms over links of the same.

This is to help make usage of the tooltip more manageable and to make room for additional functionality, as in #520.