Refactor out use of anyhow

[algesten]

This relates to webrtc-rs/webrtc#106

On macOS, the following tests stall. They are stalling also before the changes of this PR.

test agent::agent_test::test_agent_restart_both_side has been running for over 60 seconds
test agent::agent_test::test_lite_lifecycle has been running for over 60 seconds
test agent::agent_test::test_run_task_in_connection_state_callback has been running for over 60 seconds
test agent::agent_test::test_run_task_in_selected_candidate_pair_change_callback has been running for over 60 seconds
test agent::agent_transport_test::test_conn_stats has been running for over 60 seconds
test mdns::mdns_test::test_multicast_dns_mixed_connection has been running for over 60 seconds
test mdns::mdns_test::test_multicast_dns_only_connection has been running for over 60 seconds

[rainliu]

@algesten, some test error in Github Actions:

---- url::url_test::test_parse_url_failure stdout ----
thread 'url::url_test::test_parse_url_failure' panicked at 'assertion failed: `(left == right)`
  left: `"parse url: relative URL without a base"`,
 right: `"relative URL without a base"`: testCase: ':::', expected err 'relative URL without a base', but got err 'parse url: relative URL without a base'', src/url/url_test.rs:132:13

[codecov]

Codecov Report

Merging #15 (415ce13) into main (2e379c8) will decrease coverage by 0.38%.
The diff coverage is 19.56%.

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
- Coverage   60.91%   60.52%   -0.39%     
==========================================
  Files          34       34              
  Lines        5692     5723      +31     
  Branches     1630     1629       -1     
==========================================
- Hits         3467     3464       -3     
- Misses        713      746      +33     
- Partials     1512     1513       +1     

Impacted Files	Coverage Δ
examples/ping_pong.rs	0.00% <0.00%> (ø)
src/agent/agent_gather_test.rs	57.73% <0.00%> (+0.37%)	⬆️
src/candidate/candidate_host.rs	80.76% <ø> (ø)
src/candidate/candidate_peer_reflexive.rs	80.00% <0.00%> (ø)
src/candidate/candidate_relay.rs	81.25% <0.00%> (ø)
src/candidate/candidate_server_reflexive.rs	80.00% <0.00%> (ø)
src/control/control_test.rs	60.71% <0.00%> (-1.68%)	⬇️
src/lib.rs	100.00% <ø> (ø)
src/mdns/mdns_test.rs	62.74% <0.00%> (ø)
src/network_type/network_type_test.rs	65.78% <ø> (ø)
... and 16 more

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