Update all the things.

[Stebalien]

secio

• Do the handshake synchronously. This means we'll never see a connection until it has actually been fully verified. It should also prevent us from blocking when checking the remote peer's ID.

conn, transports, etc.

• Accept concurrently. This prevents synchronous secio handshakes from blocking
  other secio handshakes.
• Use contexts for timeouts. One can now accurately set dial contexts via timeouts instead of setting a global dial timeout. We still have a global 60s dial timeout for sanity.
• Correctly set the source address.

reuseport

• Move away from syscall to sys. This should fix support on some platforms, e.g., linux-arm64.
• Make reuseport compile on netbsd
• Make checking for reuseport support faster.
• Probably more...

go-msgio/mpool

• Remove the locks and allocate pools up front (much faster). They're not that large.
• Update multiple dependent packages to share a global msgio buffer pool instead of copying it. I'm not entirely sure how we weren't deadlocking and panicking all over the place; we were copying locks.

cmds, cmdkit

• Rename DefaultVal -> Default, Default -> WithDefault

Depends on ipfs/go-ipfs-cmds#17

[whyrusleeping]

Damn, this should be a good update.

[Stebalien]

• Merge remove all instances of Default(false) #4042 first and then I'll fix this.

[whyrusleeping]

@Stebalien done did it

[Stebalien]

@whyrusleeping done.