fix(cli): Fix client IPv6 URI generation for gRPC connections

[redgoat650]

Connecting to gRPC repository API using an IPv6 address does not correctly configure the URI for the client's dial. Reconstructing the parsed URL into hostname + ":" + port will remove the square brackets required for IPv6 addressing, resulting in a too many colons in address error.

Fix the issue by instead using the helper net.JoinHostPort(), which will add square brackets for IPv6 hostnames.

Tested by running TestServer with httptest.serve flag set, forcing the test server to listen on the IPv6 loopback:

cd internal/server
go test -v -run=TestServer$ --httptest.serve=[::1]:0 ./server

Fails without fix:

    server_test.go:48: 
                Error Trace:    /workspaces/kopia/internal/server/server_test.go:48
                Error:          Received unexpected error:
                                failed to exit idle mode: invalid target address ::1:45373, error info: address ::1:45373:443: too many colons in address

Passes with fix:

--- PASS: TestServer (0.81s)
PASS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.06%. Comparing base (cb455c6) to head (9c6e238).
Report is 121 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3830      +/-   ##
==========================================
+ Coverage   75.86%   77.06%   +1.19%     
==========================================
  Files         470      476       +6     
  Lines       37301    28682    -8619     
==========================================
- Hits        28299    22104    -6195     
+ Misses       7071     4684    -2387     
+ Partials     1931     1894      -37     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[julio-lopez]

@redgoat650 Should we either run
go test -v -run=TestServer$ --httptest.serve=[::1]:0 ./server in CI or add a explicit tests, for this case? probably reusing the TestServer test.