Add inspect interfaces command, refactor cmd package

[vista-]

This PR adds the inspect interfaces subcommand, which can be used to list the network interfaces of deployed nodes of a lab. The command provides information about the operational state, type, and interface alias of interfaces of lab nodes.

This is a privileged Containerlab command, as it requires entering network namespaces, which only privileged users can perform.

It can either output with pretty-printed table or JSON formatting.

The inspect and the new inspect interfaces command has been moved into a sub-package of cmd.

This PR also comes with a large refactor of the cmd package, moving common (or shared) variables within the common package inside cmd.

[kaelemc]

@vista- with --format json do you think we could hide the log messages to align with clab ins -a -f json?

This just makes parsing the json a little easier so we don't have to strip out any logging

[hellt]

I think the idea with json output and log messages that we used in other commands was that log messages are directed to stderr and json was printed to stdout

[hellt]

thanks a bunch @vista-
lgtm

[codecov]

Codecov Report

Attention: Patch coverage is 73.49081% with 101 lines in your changes missing coverage. Please review.

Project coverage is 52.41%. Comparing base (515af5d) to head (6c4b5e4).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/inspect/inspect_interfaces.go	68.03%	59 Missing and 19 partials ⚠️
cmd/disableTxOffload.go	0.00%	6 Missing ⚠️
cmd/config.go	20.00%	4 Missing ⚠️
cmd/inspect/inspect.go	81.81%	2 Missing and 2 partials ⚠️
cmd/config_template.go	0.00%	3 Missing ⚠️
cmd/exec.go	81.81%	1 Missing and 1 partial ⚠️
cmd/root.go	90.00%	1 Missing and 1 partial ⚠️
cmd/generate.go	75.00%	0 Missing and 1 partial ⚠️
cmd/save.go	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2437      +/-   ##
==========================================
+ Coverage   52.16%   52.41%   +0.24%     
==========================================
  Files         171      172       +1     
  Lines       17342    17582     +240     
==========================================
+ Hits         9047     9215     +168     
- Misses       7346     7398      +52     
- Partials      949      969      +20     

Files with missing lines	Coverage Δ
clab/config.go	68.16% <100.00%> (+0.06%)	⬆️
cmd/deploy.go	76.84% <100.00%> (ø)
cmd/destroy.go	77.77% <100.00%> (ø)
cmd/graph.go	39.25% <100.00%> (ø)
cmd/redeploy.go	90.62% <100.00%> (ø)
cmd/tools_netem.go	70.87% <100.00%> (ø)
cmd/tools_veth.go	72.78% <100.00%> (ø)
types/types.go	62.88% <ø> (ø)
cmd/generate.go	68.24% <75.00%> (ø)
cmd/save.go	73.33% <90.00%> (ø)
... and 7 more

... and 1 file with indirect coverage changes