Fix Mark-Range command: ensure that NS Favorite doesn't exceed the limit

[rtim75]

Fixes #1191

While the root cause of the issue, where the number of favorites exceeds the limit, is still unknown, I believe this is a nice check to have, when validating namespaces. And as pointed out in the #1191, it fixes the issue with mark-range not working and instead showing in the tooltip the namespace that exceeds the limit.

• Increased the MaxFavoritesNS to cover all 0-9 numbers.
• Tests are updated

Manually validated that configs are updating properly and the number of favorites doesn't exceed the limit.

Tested on MacOs.

> make test
?       github.com/derailed/k9s [no test files]
?       github.com/derailed/k9s/internal/config/mock    [no test files]
ok      github.com/derailed/k9s/cmd     3.981s
ok      github.com/derailed/k9s/internal        0.618s
ok      github.com/derailed/k9s/internal/client 1.895s
ok      github.com/derailed/k9s/internal/color  4.033s
ok      github.com/derailed/k9s/internal/config 1.241s
ok      github.com/derailed/k9s/internal/config/data    2.608s
ok      github.com/derailed/k9s/internal/config/json    4.345s
?       github.com/derailed/k9s/internal/perf   [no test files]
ok      github.com/derailed/k9s/internal/dao    1.324s
ok      github.com/derailed/k9s/internal/health 0.259s
?       github.com/derailed/k9s/internal/render/helm    [no test files]
ok      github.com/derailed/k9s/internal/model  4.526s
ok      github.com/derailed/k9s/internal/model1 1.220s
ok      github.com/derailed/k9s/internal/port   0.687s
ok      github.com/derailed/k9s/internal/render 2.912s
ok      github.com/derailed/k9s/internal/tchart 1.612s
ok      github.com/derailed/k9s/internal/ui     1.385s
ok      github.com/derailed/k9s/internal/ui/dialog      3.250s
ok      github.com/derailed/k9s/internal/view   2.166s
ok      github.com/derailed/k9s/internal/view/cmd       0.608s
ok      github.com/derailed/k9s/internal/vul    3.068s
ok      github.com/derailed/k9s/internal/watch  4.615s
ok      github.com/derailed/k9s/internal/xray   4.032s

[derailed]

@rtim75 Good catch! Thank you for this update!