✨ Support deduplication when using ClusterctlConfig

[furkatgofurov7]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):

Special notes for your reviewer:
If new provider is added through clusterctlconfig:

1. which does not exist in the current config map it will be added as new entry to configmap
2. with new URL and if provider exists, it only updates the URL of that entry
3. without any changes to URL and if provider exists, it stays as is without any changes.

I am planning to add tests as a follow up PR, since config.go anyways did not have a dedicated test file up until now.

Checklist:

• squashed commits into logical changes
• includes documentation
• adds unit tests
• adds or updates e2e tests

[Danil-Grigorev]

Can you please add unit tests for the PR? Also you mentioned some kind of issue with bootstrap or control plane provider? Is this resolved? I see no changes since last commit @furkatgofurov7

LGTM otherwise

[alexander-demicev]

I removed "fixes" from the PR description so issue doesn't close. Tests can be added in a follow-up PR.

[furkatgofurov7]

Can you please add unit tests for the PR? Also you mentioned some kind of issue with bootstrap or control plane provider? Is this resolved? I see no changes since last commit @furkatgofurov7

LGTM otherwise

No issues with bootstrap after I tested it properly and it is resolved. I will open a follow-up with unit tests addition.