01e2830 [net] Remove unnecessary default args on CNode constructor (Amiti Uttarwar)
bc5d65b [refactor] Remove IsOutboundDisconnectionCandidate (Amiti Uttarwar)
2f2e13b [net/refactor] Simplify multiple-connection checks (Amiti Uttarwar)
7f7b83d [net/refactor] Rework ThreadOpenConnections logic (Amiti Uttarwar)
35839e9 [net] Fix bug where AddrFetch connections would be counted as outbound full relay (Amiti Uttarwar)
4972c21 [net/refactor] Clarify logic for selecting connections in ThreadOpenConnections (Amiti Uttarwar)
60156f5 [net/refactor] Remove fInbound flag from CNode (Amiti Uttarwar)
7b322df [net/refactor] Remove m_addr_fetch member var from CNode (Amiti Uttarwar)
1492342 [net/refactor] Remove fFeeler flag from CNode (Amiti Uttarwar)
49efac5 [net/refactor] Remove m_manual_connection flag from CNode (Amiti Uttarwar)
d3698b5 [net/refactor] Add connection type as a member var to CNode (Amiti Uttarwar)
46578c0 [doc] Describe different connection types (Amiti Uttarwar)
442abae [net/refactor] Add AddrFetch connections to ConnectionType enum (Amiti Uttarwar)
af59feb [net/refactor] Extract m_addr_known logic from initializer list (Amiti Uttarwar)
e1bc298 [net/refactor] Add block relay only connections to ConnectionType enum (Amiti Uttarwar)
0e52a65 [net/refactor] Add feeler connections to ConnectionType enum (Amiti Uttarwar)
1521c47 [net/refactor] Add manual connections to ConnectionType enum (Amiti Uttarwar)
26304b4 [net/refactor] Introduce an enum to distinguish type of connection (Amiti Uttarwar)
3f1b714 scripted-diff: Rename OneShot to AddrFetch (Amiti Uttarwar)

Pull request description:

  **This is part 1 of bitcoin#19315, which enables the ability to test `outbound` and `block-relay-only` connections from the functional tests.** Please see that PR for more information of overall functionality.

  **This PR simplifies how we manage different connection types.** It introduces an enum with the various types of connections so we can explicitly define the connection type. The existing system relies on a series of independent flags, then has asserts scattered around to ensure that conflicting flags are not enabled at the same time. I find this approach to be both brittle and confusing. While making these changes, I found a small bug due to the silent assumptions.

  This PR also proposes a rename from `OneShot` to `AddrFetch`. I find the name `OneShot` to be very confusing, especially when we also have `onetry` manual connections. Everyone I've talked to offline has agreed that the name is confusing, so I propose a potential alternative. I think this is a good opportunity for a rename since I'm creating an enum to explicitly define the connection types.
  (some context for the unfamiliar: `oneshot` or `addrfetch` connections are short-lived connections created on startup. They connect to the seed peers, send a `getaddr` to solicit addresses, then close the connection.)

  Overview of this PR:
  * rename `oneshot` to `addrfetch`
  * introduce `ConnectionType` enum
  * one by one, add different connection types to the enum
  * expose the `conn_type` on CNode, and use this to reduce reliance on flags (& asserts)
  * fix the bug in counting different type of connections
  * some additional cleanup to simplify logic and make expectations explicit/inclusive rather than implicit/exclusive.

ACKs for top commit:
  jnewbery:
    utACK 01e2830
  laanwj:
    Code review ACK 01e2830, the commits are pretty straightforward to follow, and I think this is a move in the right direction overall
  vasild:
    ACK 01e2830
  sdaftuar:
    ACK 01e2830.
  fanquake:
    ACK 01e2830 - I don't have as much experience with the networking code but these changes look fairly straight forward, the new code seems more robust/understandable and the additional documentation is great. I'm glad that a followup branch is already underway. There might be some more review comments here later today, so keep an eye on the discussion, however I'm going to merge this now.
  jb55:
    wow this code was messy before... ACK 01e2830

Tree-SHA512: 7bb644a6ed5849913d777ebc2ff89133ca0fbef680355a9a344e07496a979e6f9ff21a958e8eea93dcd7d5c343682b0c7174b1a3de380a4247eaae73da436e15