DRKey ported from previous SCIONLab branch

Squashed changes for DRKey, ported to latest upstream master branch.

This includes the following main commits:

* 707a5e6 DRKey ported from the old SCIONLab (netsec-ethz#77)

  This is itself a squashed commit  containing the bulk of the newly
  added DRKey implementation.

* 5a623a2 Allow a second call to initQUICSockets. (netsec-ethz#79)
* df3a258 unify personal annotations to JordiSubira (netsec-ethz#80)
* 9380c76 fix Level 1 key Exchange (netsec-ethz#81)

  Add sanity check in the drkey_fetcher which validates that the
  response srcIA matches the intended server IA.

* a90f354 Remove redundant fields from Lvl1Req/Resp (netsec-ethz#83)
* 64f4c23 cs/drkey: handle situations where no path to a peer AS can be found (netsec-ethz#90)

  This condition is now handled analog to a similar condition in
  github.com/scionproto/scion/go/pkg/trust.AuthRouter.ChooseServer

The main change applied to make this compatible with the master
branch was to resolve the renaming / moving of what was previously
pkg/sciond to now pkg/daemon.

Co-authored-by: JordiSubira <[email protected]>
Co-authored-by: Juan A. Garcia Pardo <[email protected]>

README: what's this fork (netsec-ethz#76)

Add description of what this fork is about, clarify where to contribute and where to find docs.
Point badges to information about this fork.

gateway: simplify defaults for policy file config (scionproto#3941)

The interpretation of the configured `ip_routing_policy_file`
configuration option was:
- if the value is identical to the default file path and the file does
  not exist, ignore it and return a default routing policy
- otherwise, read the file at the specified location (and fail if it
  doesn't exist)

Not only does this seem a bit convoluted, but it can also fail in
interesting ways; when the user does not want to specify an
`ip_routing_policy_file` and there is an error stat-ing the file at the
default location (e.g. no permission to read directory, error while
accessing network file system, etc.), the SIG would refuse to start.

Simplified to only handle the empty value as special default.
The consequence of this is that the configuration files now _must_
specify the `ip_routing_policy` file path if it should be loaded.

Also, removed the default for the `traffic_policy_file` option, making
this option mandatory in the configuration file.

Finally, removed the unused `dispatcher` configuration entry.

Allow clock drifts up to 10. (netsec-ethz#58)

In SCIONLab the clocks are not well synchornized. We allow up to 10 seconds difference
among clocks in different machines.
This particular patch relies on  instead of modifying the
default values.

(cherry picked from commit 692af45)

Release 0.5.0

Bazel: Use --stamp command line flag (scionproto#3380)

This fixes the problem introduced by new version of go_rules,
the symptom being that StartupVersion was not set properly.

snet: Use correct base conn (scionproto#3134)

This PR makes the reader and writer conn of snet to point to the correct
base conn.

fixes scionproto#3133

Fix deadlock in memrevcache (scionproto#1895)

The current memrevcache code will deadlock on Insert, every time: Insert
takes the write lock at the top, and later calls Get, which tries to get
the read lock. This is an automatic deadlock.

Also:
- Fix some log identifiers in go PS handlers.

PS: Add missing initialization of config (scionproto#1882)

Fix overlay port handling for BR in topology. (scionproto#1799)

It is (currently) illegal to specify `OverlayPort` in a BR entry, as the
BR doesn't run on top of the dispatcher. Additionally, calling
`OverlayAddr` on the internal address of a BR should set the overlay
port appropriately (assuming a UDP-based overlay).