Fixed seeds update for 27.0

[achow101]

The ipv4 and ipv6 seeds are updated from sipa's crawler, as outlined in contrib/seeds/README.md. The onion and i2p seeds are pulled from my node's addrman using getrawaddrman and then a connection was made to each node to retrieve the current service flags, block height, and user agent string before filtering through makeseeds.py. The CJDNS nodes were not updated as my node is not connected to that network.

makeseeds.py is also updated for more recent user agent strings as well as being able to handle i2p addresses.

Also updated the testnet seeds.

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ACK	fanquake

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[fanquake]

I've tested this on mainnet:

# no anchors or peers, dns=0 dnsseed=0
2024-03-06T11:01:47Z opencon thread start
2024-03-06T11:01:47Z Adding fixed seeds as -dnsseed=0 (or IPv4/IPv6 connections are disabled via -onlynet) and neither -addnode nor -seednode are provided
2024-03-06T11:01:47Z Added 801 fixed seeds from reachable networks.
2024-03-06T11:01:56Z New outbound-full-relay v1 peer connected: version: 70016, blocks=833398, peer=0
2024-03-06T11:01:56Z Synchronizing blockheaders, height: 833398 (~100.00%)

but testnet doesn't work:

# no anchors or peers, dns=0 dnsseed=0
2024-03-06T10:59:25Z opencon thread start
2024-03-06T10:59:26Z Adding fixed seeds as -dnsseed=0 (or IPv4/IPv6 connections are disabled via -onlynet) and neither -addnode nor -seednode are provided
2024-03-06T10:59:26Z Added 0 fixed seeds from reachable networks.

Although it looks like this was already broken #29574.

[willcl-ark]

In cross-referencing one of my own nodes (as the only ones I can really do any cross-checking on) I notice that the data returned for them from sipa's seeder (for my node) does not match what I expect in two ways:

1. Incorrect version string: reported as 24.0 rather than 26.0. The version is reported correctly to me by another instance of bitcoind connecting to the node.
2. Low uptime: this node has been running uninterrupted (and without fault) since early December, after being updated to v26.0. Before that it ran uninterrupted since the last major version update. Connectivity reported as <=30% does not feel congruent with its uptime.

My interpretation therefore is that it's possible that, if anything, we may be missing out on adding more seed nodes to this list?

In any case, the results of a single node likely don't affect the general accuracy of the changes here and I suppose the changes proposed here are probably correct on balance.

[fanquake]

ACK 7ab5439

Although it looks like this was already broken #29574.

Given the discussion, not considering this a blocker given it's not a regression (and we can still backport a change that introduces new seeds to 27.x if we want to).