Fix architecture diagram arrow directions

Arrows should signify "calls" or "generates" unless noted.

Author: jkczyz

ARCH.md

@@ -37,14 +37,14 @@ At a high level, some of the common interfaces fit together as follows:
                      -----------------
                      | KeysInterface |  --------------
                      -----------------  | UserConfig |
-         --------------------       |   --------------
-   ------| MessageSendEvent |       |   |     ----------------
+         --------------------       ^   --------------
+   ------| MessageSendEvent |       |   ^     ----------------
   /      --------------------       |   |     | FeeEstimator | <-----------------------
  |   (as MessageSendEventsProvider) |   |     ----------------                         \
- |                         ^        |   |    /                ------------------------  |
+ |                         ^        |   |    ^                ------------------------  |
  |                          \       |   |   /      ---------> | BroadcasterInterface |  |
  |                           \      |   |  /      /           ------------------------  |
- |                            \     v   v v      /                          ^           |
+ |                            \     |   | /      /                          ^           |
  |    (as                      ------------------       ----------------    |           |
  |    ChannelMessageHandler)-> | ChannelManager | ----> | chain::Watch |    |           |
  v               /             ------------------       ----------------    |           |
@@ -54,8 +54,8 @@ At a high level, some of the common interfaces fit together as follows:
  |                    -----------------        \       _----------------   /           /
  |                    | chain::Access |         \     / | ChainMonitor |---------------
  |                    -----------------          \   /  ----------------
- |                            |                   \ /          |
-(as RoutingMessageHandler)    v                    v           v
+ |                            ^                   \ /          |
+(as RoutingMessageHandler)    |                    v           v
   \                   ----------------------   ---------   -----------------
    -----------------> | NetGraphMsgHandler |   | Event |   | chain::Notify |
                       ----------------------   ---------   -----------------