Regenerate fallback list for 0.2.9

We need to regenerate the fallback directory mirror list in 0.2.9 in case any of the 0.2.8 fallbacks have changed details or gone down.

This should not require another opt-in mailout, as we had ~70 additional fallbacks in 0.2.8 that were suitable but not selected.

We should also:

• restore the 120 day stability period and 99% uptime requirement that were reduced in 0.2.8 due to #18050 (moved)
• check the bandwdith range in the script's generated C comments
• check the IP version, netblock, port, and Exit flag proportions in the script's stderr output

Over the longer term, we could:

• reconsider whether to allow 2 fallbacks per operator (contact, family), while keeping 1 per IP
• decide whether to change to an opt-out system, where we includes fallbacks unless operators specifically opt-out