Update kube context with certmap info if necessary

[vuil]

Since the cert data and skip verify intent is captured in the certmap for the endpoint that one tanzu logins to, subsequent tanzu login to the same endpoint can succeed without providing these values. However the kube context created with the subsequent login attempt does not incorporate these values when they originate from the cert map.

This change addresses this inconsistency, by ensuring that these values are incorporated unless command line arguments of alternative ones are provided in the login command.

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Describe testing done for PR

Updated and ran unit tests

Also manually tested with following

first establish successfully login with

tanzu login --endpoint https://tpsm-host --endpoint-ca-certificate ~/myca.crt 
OR
tanzu login --endpoint https://tpsm-host  --insecure-skip-tls-verify

then test with

tanzu context delete -y tpsm-ef5efcd6; ./bin/tanzu login --endpoint https://tpsm-host; tanzu project use xxx; tanzu space list

[i] Refreshing plugin inventory cache for "projects.packages.broadcom.com/tanzu_cli/plugins/plugin-inventory:latest", this will take a few seconds.
[i] Reading plugin inventory for "projects.packages.broadcom.com/tanzu_cli/plugins/plugin-inventory:latest", this will take a few seconds.
[i] Deleting kubeconfig context 'tanzu-cli-tpsm-ef5efcd6:xxx' from the file '/Users/vuichiap/.config/tanzu/kube/config'
[ok] Successfully deleted context "tpsm-ef5efcd6"
[i] Opening the browser window to complete the login
Log in by visiting this link:

    https://tpsm-host/auth/oauth/authorize?client_id=tp_cli_app&code_challenge=sV_qnOMk4CG...

    Optionally, paste your authorization code: [...]


[ok] Successfully logged in to 'https://tpsm-airgap-bugbash.acc.broadcom.net' and created a tanzu context
✓ Successfully set project to xxx

prior to fix, this follows:

Error: failed to get API group resources: unable to retrieve the complete list of server APIs: spaces.tanzu.vmware.com/v1alpha1: Get "https://tpsm-airgap-bugbash.acc.broadcom.net/org/2b96f0c0-e25c-4f93-868d-41285e8e0dc4/project/7ae590c2-3f5b-4aee-9e03-85c2dc28ef56/apis/spaces.tanzu.vmware.com/v1alpha1": tls: failed to verify certificate: x509: certificate signed by unknown authority

after fix, tanzu space works as expected:

Listing spaces from organization yyyyyyyyyyy, project xxx
  NAME                         STATUS     PROFILES RESOLVED  REPLICAS  AGE
  accelerator-test             Ready      2/2                1/1       28h
...

Release note

kubecontext constructed on successful `tanzu login` will incorporate custom cert or skip verification flag from the cert map if neither are explicitly provided in the command invocation

Additional information

Special notes for your reviewer

[prkalle]

LGTM. Thanks for the changes!