feat: allow to get the network address server is listening on

[haoqixu]

Add an Addr() method to fetch the network address Server is listening on. I think this may be useful for the supervisor to start a server with 0 port to allocate an ephemeral port and get the allocated port for rendering an agent config.

[codecov]

Codecov Report

Attention: 129 lines in your changes are missing coverage. Please review.

Comparison is base (efddaa2) 76.11% compared to head (6d08f1f) 72.50%.
Report is 31 commits behind head on main.

Files	Patch %	Lines
internal/certs.go	0.00%	118 Missing ⚠️
client/internal/httpsender.go	88.00%	2 Missing and 1 partial ⚠️
client/internal/mockserver.go	85.71%	2 Missing and 1 partial ⚠️
server/httpconnection.go	0.00%	2 Missing ⚠️
client/internal/clientcommon.go	90.90%	1 Missing ⚠️
client/internal/packagessyncer.go	0.00%	1 Missing ⚠️
server/serverimpl.go	95.65%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
- Coverage   76.11%   72.50%   -3.62%     
==========================================
  Files          24       25       +1     
  Lines        1834     2022     +188     
==========================================
+ Hits         1396     1466      +70     
- Misses        326      446     +120     
+ Partials      112      110       -2     

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

[tigrannajaryan]

I think this is a good idea.

[tigrannajaryan]

Thank you @haoqixu !