chore: merging user service with connection manager

[iamayushm]

Description

1. Earlier we use to pass token in getConnection() function in "github.com/devtron-labs/devtron/client/argocdServer/connection" from outside, now we will be reading token inside getConnection func from outside.

2. For achieving point 1, argocdUserService is merged with argocdConnectionManager

3. All usages for setting argoCD token in context is removed

4. For resolving some circular imports, one method is refactored into clusterReadService, all it's usages are changed and some things are moved into bean.

Future refactoring scope:-

1. passing authConfig as argument to getConnection function
2. caching connection object
3. passing config() in getConnection function from outside

Checklist:

• The title of the PR states what changed and the related issues number (used for the release note).
• Does this PR requires documentation updates?
• I've updated documentation as required by this PR.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have tested it for all user roles.
• I have added all the required unit/api test cases.

Does this PR introduce a user-facing change?

[sonarqubecloud]

Quality Gate passed

Issues
20 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.2% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

The migration files have successfully passed the criteria!!