refactor(cordova/apple/ios): remove reachability test

[fortuna]

The test adds too much complexity, without much value.
Most importantly, it requires the per-platform code to inspect the config, which we want to avoid.

This is a step closer to config-agnostic platform code.

I'm removing the reachability code from iOS. We can do the same cleanup on Android and outline-go-tun2socks, but I'll leave that for later, since it doesn't block the config work.

/cc @bi-kh @daniellacosse @sbruens

[codecov]

Codecov Report

Patch coverage: 84% and no project coverage change.

Comparison is base (6e5bfef) 36% compared to head (d344d65) 36%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #1663   +/-   ##
======================================
  Coverage      36%     36%           
======================================
  Files          46      45    -1     
  Lines        2815    2756   -59     
  Branches      314     312    -2     
======================================
- Hits         1018    1006   -12     
+ Misses       1797    1750   -47     

Flag	Coverage Δ
apple	14% <ø> (+<1%)	⬆️
ios	15% <ø> (+<1%)	⬆️
macos	14% <ø> (+<1%)	⬆️
unittests	36% <84%> (+<1%)	⬆️
www	45% <84%> (+<1%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...eLib/Sources/OutlineTunnelSources/OutlineVpn.swift	0% <ø> (ø)
...PacketTunnelProviderSources/PacketTunnelProvider.m	0% <ø> (ø)
...ib/Tests/OutlineTunnelTest/OutlineTunnelTest.swift	100% <ø> (ø)
src/www/app/app.ts	8% <0%> (+<1%)	⬆️
src/www/app/outline_server_repository/index.ts	73% <ø> (-1%)	⬇️
src/www/app/outline_server_repository/server.ts	34% <ø> (+<1%)	⬆️
src/www/app/platform.ts	100% <ø> (ø)
src/www/model/server.ts	100% <ø> (ø)
...erver_repository/outline_server_repository.spec.ts	100% <100%> (ø)

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