Update the default issuer to TCSP

[prkalle]

What this PR does / why we need it

This PR updates the hardcode default issuer to TCSP. This values will only be used when reading the issuer from the centralconfig DB fails.

Which issue(s) this PR fixes

Fixes #

Describe testing done for PR

Removed the below 2 entries from the local centralconfig DB cache(~/.cache/tanzu/plugin_inventory/default/central_config.yaml) and tested login. I could successfully login using the TCSP issuer.

cli.core.tanzu_default_csp_metadata:
  issuerStaging: https://console-stg.tanzu.broadcom.com/csp/gateway/am/api
  issuerProduction: https://console.tanzu.broadcom.com/csp/gateway/am/api

login command is rightly using the TCSP issuer URL as shown below

❯ ./bin/tanzu login --staging --endpoint https://api.tanzu-dev.cloud.vmware.com
[i] Opening the browser window to complete the login
Log in by visiting this link:

    https://console-stg.tanzu.broadcom.com/csp/gateway/discovery?client_id=tanzu-cli-client-id&code_challenge=yeHHFyJiFsK7ensf5BvpQE5-Mp843nlbFYt5ROoCenM&code_challenge_method=S256&redirect_uri=http%3A%2F%2F127.0.0.1%3A65492%2Fcallback&response_type=code&state=308bcacfce46038b2e542f93fc3bcc33

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


[ok] Successfully logged into 'Falcons' organization and created a tanzu context

Release note

Additional information

Special notes for your reviewer

[anujc25]

LGTM. Thanks @prkalle