Shell autocomplete functions do not work correctly

[waddles]

Describe the bug
k9s includes shell autocompletion commands that appear to have been taken directly from kubectl except they don't work as expected.

I work with a number of contexts and switching between them, especially with OIDC, is quite slow. I prefer to start k9s with a --context flag to select my desired context upon startup but the lack of completion suggestions is frustrating.

The undocumented __complete autocomplete suggestions command only works to suggest the top level functions but does not work for suggesting options to double-dash parameters like --context.

To Reproduce

% k9s __complete ""
completion	Generate the autocompletion script for the specified shell
help	Help about any command
info	List K9s configurations info
version	Print version/build info
:4
Completion ended with directive: ShellCompDirectiveNoFileComp

% k9s __complete - ""
:0
Completion ended with directive: ShellCompDirectiveDefault

% k9s __complete --context ""
:0
Completion ended with directive: ShellCompDirectiveDefault

Furthermore the command suggests that --completion, --help, --info, --version should also work but they end in a panic except for --help. [EDIT: - this is an incorrect statement but k9s should handle incorrect flags without panicking]

% k9s __complete -- ""
completion	Generate the autocompletion script for the specified shell
help	Help about any command
info	List K9s configurations info
version	Print version/build info
:4
Completion ended with directive: ShellCompDirectiveNoFileComp

% k9s --version
Error: unknown flag: --version
[-snipped-]
panic: unknown flag: --version

goroutine 1 [running]:
github.com/derailed/k9s/cmd.Execute(...)
	github.com/derailed/k9s/cmd/root.go:60
main.main()
	github.com/derailed/k9s/main.go:32 +0x3c

Expected behavior
k9s should be able to suggest completion options for flags the same way kubectl does, eg.

% kubectl __complete --user ""
local
oidc
:4
Completion ended with directive: ShellCompDirectiveNoFileComp

% k9s __complete --user ""
:0
Completion ended with directive: ShellCompDirectiveDefault

and

% kubectl __complete --context ""
microk8s
k3s
:4
Completion ended with directive: ShellCompDirectiveNoFileComp

% k9s __complete --context ""
:0
Completion ended with directive: ShellCompDirectiveDefault

Versions:

Seems to affect all versions

% k9s version
 ____  __.________
|    |/ _/   __   \______
|      < \____    /  ___/
|    |  \   /    /\___ \
|____|__ \ /____//____  >
        \/            \/

Version:    v0.31.5
Commit:     ff17fff2861c02d325fc95d536d3787b83cb3782
Date:       2024-01-12T22:03:40Z

Additional context
It took me quite a while to work out that the output from k9s completion zsh actually calls k9s __complete <flags> "string" to get its suggestions.