Merge bitcoin/bitcoin#33770: init: Require explicit -asmap filename

288b8c30be doc: Drop (default: none) from -i2psam description (Ryan Ofsky)
f6ec3519a3 init: Require explicit -asmap filename (Ryan Ofsky)

Pull request description:

  Currently, if `-asmap` is specified without a filename bitcoind tries to load `ip_asn.map` data file.

  This change now requires `-asmap=ip_asn.map` or another filename to be specified explicitly.

  The change is intended to make behavior of the option explicit and avoid confusion reported https://github.com/bitcoin/bitcoin/issues/33386 where documentation specifies a default file which is not actually loaded by default. It was originally implemented in
  https://github.com/bitcoin/bitcoin/pull/33631#issuecomment-3410302383 and various alternatives are discussed there.

ACKs for top commit:
  brunoerg:
    reACK 288b8c30be
  fjahr:
    re-ACK 288b8c30be
  vostrnad:
    utACK 288b8c30be
  achow101:
    ACK 288b8c30be

Tree-SHA512: 11a38a03892a58d6ccc1505cfbf915f58a86df9891761d89dc54b92d40593ee3cbb2d7c7bdbb922b871b3529072ef7f34cc98393aff6e8f0633b56352315b27c

doc/files.md

@@ -66,7 +66,6 @@ Subdirectory       | File(s)               | Description
 `./`               | `debug.log`           | Contains debug information and general logging generated by `bitcoind` or `bitcoin-qt`; can be specified by `-debuglogfile` option
 `./`               | `fee_estimates.dat`   | Stores statistics used to estimate minimum transaction fees required for confirmation
 `./`               | `guisettings.ini.bak` | Backup of former [GUI settings](#gui-settings) after `-resetguisettings` option is used
-`./`               | `ip_asn.map`          | IP addresses to Autonomous System Numbers (ASNs) mapping used for bucketing of the peers; path can be specified with the `-asmap` option
 `./`               | `mempool.dat`         | Dump of the mempool's transactions
 `./`               | `onion_v3_private_key` | Cached Tor onion service private key for `-listenonion` option
 `./`               | `i2p_private_key`     | Private key that corresponds to our I2P address. When `-i2psam=` is specified the contents of this file is used to identify ourselves for making outgoing connections to I2P peers and possibly accepting incoming ones. Automatically generated if it does not exist.

doc/release-notes-33770.md

@@ -0,0 +1,4 @@
+`-asmap` requires explicit filename
+-----------------------------------
+
+In previous releases, if `-asmap` was specified without a filename, this would try to load an `ip_asn.map` data file. Now loading an asmap file requires an explicit filename like `-asmap=ip_asn.map`. This change was made to make the option easier to understand, because it was confusing for there to be a default filename not actually loaded by default (https://github.com/bitcoin/bitcoin/issues/33386). Also this change makes the option more future-proof, because in upcoming releases, specifying `-asmap` will load embedded asmap data instead of an external file (https://github.com/bitcoin/bitcoin/pull/28792).