config: backport the rename of fastsync to blocksync (#9259)

This is largely a cherry pick of #6755 with some additional fixups added where detected. 
This change moves the blockchain package to a package called blocksync. Additionally, it renames the relevant uses of the term `fastsync` to `blocksync`.

closes: #9227 

#### PR checklist

- [ ] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

test/e2e/networks/ci.toml

@@ -63,10 +63,10 @@ abci_protocol = "builtin"
 perturb = ["pause"]
 
 [node.validator05]
+block_sync = "v0" 
 start_at = 1005 # Becomes part of the validator set at 1010
 seeds = ["seed02"]
 database = "cleveldb"
-fast_sync = true
 mempool_version = "v1"
 # FIXME: should be grpc, disabled due to https://github.com/tendermint/tendermint/issues/5439
 #abci_protocol = "grpc"
@@ -76,7 +76,7 @@ perturb = ["kill", "pause", "disconnect", "restart"]
 [node.full01]
 start_at = 1010
 mode = "full"
-fast_sync = true
+block_sync = "v0"
 persistent_peers = ["validator01", "validator02", "validator03", "validator04", "validator05"]
 retain_blocks = 1
 perturb = ["restart"]
@@ -84,7 +84,7 @@ perturb = ["restart"]
 [node.full02]
 start_at = 1015
 mode = "full"
-fast_sync = true
+block_sync = "v0"
 state_sync = true
 seeds = ["seed01"]
 perturb = ["restart"]
@@ -97,4 +97,4 @@ persistent_peers = ["validator01", "validator02", "validator03"]
 [node.light02]
 mode= "light"
 start_at= 1015
-persistent_peers = ["validator04", "full01", "validator05"]
+persistent_peers = ["validator04", "full01", "validator05"]