feat(rpc): Added RPC cleardiscouraged (#5273)

## Issue being fixed or feature implemented


## What was done?
Added RPC `cleardiscouraged` which clears internally the list of
discouraged peers.

Note: Implementation of a `listdiscouraged` RPC is not possible because
the internal data structure used for discouraged peers is a Bloom
filter.

## How Has This Been Tested?

## Breaking Changes


## Checklist:
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [x] I have made corresponding changes to the documentation

**For repository code-owners and collaborators only**
- [x] I have assigned this pull request to a milestone

doc/release-notes-5273.md

@@ -0,0 +1,5 @@
+Added RPCs
+--------
+
+- `cleardiscouraged` clears all the already discouraged peers.
+

src/banman.cpp

@@ -68,6 +68,16 @@ void BanMan::ClearBanned()
     if (m_client_interface) m_client_interface->BannedListChanged();
 }
 
+void BanMan::ClearDiscouraged()
+{
+    {
+        LOCK(m_cs_banned);
+        m_discouraged.reset();
+        m_is_dirty = true;
+    }
+    if (m_client_interface) m_client_interface->BannedListChanged();
+}
+
 bool BanMan::IsDiscouraged(const CNetAddr& net_addr)
 {
     LOCK(m_cs_banned);

src/banman.h

@@ -63,6 +63,7 @@ public:
     void Ban(const CSubNet& sub_net, int64_t ban_time_offset = 0, bool since_unix_epoch = false);
     void Discourage(const CNetAddr& net_addr);
     void ClearBanned();
+    void ClearDiscouraged();
 
     //! Return whether net_addr is banned
     bool IsBanned(const CNetAddr& net_addr);

src/rpc/net.cpp

@@ -736,6 +736,27 @@ static UniValue clearbanned(const JSONRPCRequest& request)
     return NullUniValue;
 }
 
+static UniValue cleardiscouraged(const JSONRPCRequest& request)
+{
+    RPCHelpMan{"cleardiscouraged",
+               "\nClear all discouraged nodes.\n",
+               {},
+               RPCResult{RPCResult::Type::NONE, "", ""},
+               RPCExamples{
+                       HelpExampleCli("cleardiscouraged", "")
+                       + HelpExampleRpc("cleardiscouraged", "")
+               },
+    }.Check(request);
+    NodeContext& node = EnsureNodeContext(request.context);
+    if (!node.banman) {
+        throw JSONRPCError(RPC_DATABASE_ERROR, "Error: Ban database not loaded");
+    }
+
+    node.banman->ClearDiscouraged();
+
+    return NullUniValue;
+}
+
 static UniValue setnetworkactive(const JSONRPCRequest& request)
 {
     RPCHelpMan{"setnetworkactive",
@@ -825,6 +846,7 @@ static const CRPCCommand commands[] =
     { "network",            "setban",                 &setban,                 {"subnet", "command", "bantime", "absolute"} },
     { "network",            "listbanned",             &listbanned,             {} },
     { "network",            "clearbanned",            &clearbanned,            {} },
+    { "network",            "cleardiscouraged",       &cleardiscouraged,        {} },
     { "network",            "setnetworkactive",       &setnetworkactive,       {"state"} },
     { "network",            "getnodeaddresses",       &getnodeaddresses,       {"count"} },
 };