Remove genesis block hash from public API

[TheBlueMatt]

Forcing users to pass a genesis block hash has ended up being
error-prone largely due to byte-swapping questions for bindings
users. Further, our API is currently inconsistent - in
ChannelManager we take a Bitcoin::Network but in NetworkGraph
we take the genesis block hash.

Luckily NetworkGraph is the only remaining place where we require
users pass the genesis block hash, so swapping it for a Network
is a simple change.

Based on #1980

[tnull]

CI is unhappy with benchmarking ChannelMananger.

Relatedly, I wonder if BestBlock::from_genesis should really be called BestBlock::from_network?

[TheBlueMatt]

Rebased and renamed from_genesis.

[codecov-commenter]

Codecov Report

Base: 87.34% // Head: 87.22% // Decreases project coverage by -0.12% ⚠️

Coverage data is based on head (d42b9b8) compared to base (96c8507).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head d42b9b8 differs from pull request most recent head d7c818a. Consider uploading reports for the commit d7c818a to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2025      +/-   ##
==========================================
- Coverage   87.34%   87.22%   -0.12%     
==========================================
  Files         101      100       -1     
  Lines       44296    44093     -203     
  Branches    44296    44093     -203     
==========================================
- Hits        38691    38461     -230     
- Misses       5605     5632      +27     

Impacted Files	Coverage Δ
lightning/src/ln/channelmanager.rs	85.84% <ø> (-0.65%)	⬇️
lightning-background-processor/src/lib.rs	81.67% <100.00%> (ø)
lightning-rapid-gossip-sync/src/lib.rs	80.00% <100.00%> (+1.73%)	⬆️
lightning-rapid-gossip-sync/src/processing.rs	92.46% <100.00%> (-0.68%)	⬇️
lightning/src/chain/channelmonitor.rs	89.52% <100.00%> (-0.07%)	⬇️
lightning/src/chain/mod.rs	84.21% <100.00%> (ø)
lightning/src/ln/channel.rs	83.63% <100.00%> (-0.37%)	⬇️
lightning/src/ln/functional_test_utils.rs	88.70% <100.00%> (+0.26%)	⬆️
lightning/src/ln/functional_tests.rs	97.20% <100.00%> (-0.10%)	⬇️
lightning/src/ln/outbound_payment.rs	80.20% <100.00%> (+0.24%)	⬆️
... and 37 more

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[tnull]

LGTM

[valentinewallace]

LGTM after rebase

[TheBlueMatt]

Rebased.

[tnull]

Seems the rebase broke CI.

[TheBlueMatt]

Oops, sorry about that, amended:

$ git diff-tree -U1 c1f47380d d7c818a3a
diff --git a/lightning-rapid-gossip-sync/src/processing.rs b/lightning-rapid-gossip-sync/src/processing.rs
index 2ee3dcbaa..4b6de04c6 100644
--- a/lightning-rapid-gossip-sync/src/processing.rs
+++ b/lightning-rapid-gossip-sync/src/processing.rs
@@ -554,5 +554,4 @@ mod tests {
 	fn full_update_succeeds_at_the_beginning_of_the_unix_era() {
-		let block_hash = genesis_block(Network::Bitcoin).block_hash();
 		let logger = TestLogger::new();
-		let network_graph = NetworkGraph::new(block_hash, &logger);
+		let network_graph = NetworkGraph::new(Network::Bitcoin, &logger);
 
@@ -570,3 +569,2 @@ mod tests {
 		// this is the timestamp encoded in the binary data of valid_input below
-		let block_hash = genesis_block(Network::Bitcoin).block_hash();
 		let logger = TestLogger::new();
@@ -577,3 +575,3 @@ mod tests {
 		{
-			let network_graph = NetworkGraph::new(block_hash, &logger);
+			let network_graph = NetworkGraph::new(Network::Bitcoin, &logger);
 			assert_eq!(network_graph.read_only().channels().len(), 0);
@@ -587,3 +585,3 @@ mod tests {
 		{
-			let network_graph = NetworkGraph::new(block_hash, &logger);
+			let network_graph = NetworkGraph::new(Network::Bitcoin, &logger);
 			assert_eq!(network_graph.read_only().channels().len(), 0);