Merge bitcoin/bitcoin#24021: Rename and move PoissonNextSend functions

9b8dcb25b5 [net processing] Rename PoissonNextSendInbound to NextInvToInbounds (John Newbery)
ea99f5d01e [net processing] Move PoissonNextSendInbound to PeerManager (John Newbery)
bb060746df scripted-diff: replace PoissonNextSend with GetExponentialRand (John Newbery)
03cfa1b603 [refactor] Use uint64_t and std namespace in PoissonNextSend (John Newbery)
9e64d69bf7 [move] Move PoissonNextSend to src/random and update comment (John Newbery)

Pull request description:

  `PoissonNextSend` and `PoissonNextSendInbound` are used in the p2p code to obfuscate various regularly occurring processes, in order to make it harder for others to get timing-based information deterministically.

  The naming of these functions has been confusing to several people (including myself, see also #23347) because the resulting random timestamps don't follow a Poisson distribution but an exponential distribution (related to events in a Poisson process, hence the name). This PR
  - moves `PoissonNextSend()` out of `net` to `random` and renames it to `GetExponentialRand()`
  - moves `PoissonNextSendInbound()` out of `CConnman` to `PeerManager` and renames it to `NextInvToInbounds()`
  - adds documentation for these functions

  This is work by jnewbery - due to him being less active currently, I opened the PR and will address feedback.

ACKs for top commit:
  jnewbery:
    ACK 9b8dcb25b5
  hebasto:
    ACK 9b8dcb25b5, I have reviewed the code and it looks OK, I agree it can be merged.
  theStack:
    ACK 9b8dcb25b5 📊

Tree-SHA512: 85c366c994e7147f9981fe863fb9838502643fa61ffd32d55a43feef96a38b79a5daa2c4d38ce01074897cc95fa40c76779816edad53f5265b81b05c3a1f4f50

src/test/fuzz/connman.cpp

@@ -97,12 +97,6 @@ FUZZ_TARGET_INIT(connman, initialize_connman)
             [&] {
                 (void)connman.OutboundTargetReached(fuzzed_data_provider.ConsumeBool());
             },
-            [&] {
-                // Limit now to int32_t to avoid signed integer overflow
-                (void)connman.PoissonNextSendInbound(
-                        std::chrono::microseconds{fuzzed_data_provider.ConsumeIntegral<int32_t>()},
-                        std::chrono::seconds{fuzzed_data_provider.ConsumeIntegral<int>()});
-            },
             [&] {
                 CSerializedNetMsg serialized_net_msg;
                 serialized_net_msg.m_type = fuzzed_data_provider.ConsumeRandomLengthString(CMessageHeader::COMMAND_SIZE);