[Remove] Testnet3 #35779

Remove testnet3 entirely from codebase to complete deprecation process stated below. https://github.com/bitcoin/bitcoin/blob/a2e074d66ac17ca7907909bbbb563e77185a45e5/src/init.cpp#L982

Also in response to. https://github.com/bitcoin/bitcoin/issues/31975

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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35779.

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Possible places where named args for integral literals may be used (e.g. func(x, /*named_arg=*/0) in C++, and func(x, named_arg=0) in Python):

• CreateGenesisBlock(testnet4_genesis_msg, testnet4_genesis_script, 1714777860, 393743547, 0x1d00ffff, 1, 50 * COIN) in src/kernel/chainparams.cpp

^{2026-07-22 20:53:29}

This was indeed a serious and functioning PR to remove testnet3 from the codebase.

Leave closed as I just read the comments in the PR by @Sjors

Thanks

The previous attempt #31974 was closed. We're in a limbo between deprecation and deletion.