Replace Nest to Elastic.Clients.Elasticsearch

[Alirexaa]

What this PR does / why we need it:

using Elastic.Clients.Elasticsearch package instead of deprecated Nest package

Which issue(s) this PR fixes:

Please reference the issue this PR will close: #2236

Special notes for your reviewer:

this PR brings the following breaking changes:

• Users that use the Nest package Public API without directly referencing this package.

• Change UseApiKey Public API

• public ElasticsearchOptions UseApiKey(ApiKeyAuthenticationCredentials apiKey);

• public ElasticsearchOptions UseApiKey(string apiKey);

• Remove ApiKeyAuthenticationCredentials Public API, Because this type is part of Nest package

• public ApiKeyAuthenticationCredentials? ApiKeyAuthenticationCredentials { get; private set; }

+public string? ApiKey { get; private set; }

**Does this PR introduce a user-facing change?**:
Yes.
Please make sure you've completed the relevant tasks for this PR, out of the following list:

- [X] Code compiles correctly
- [X] Created/updated tests
- [X] Unit tests passing
- [ ] End-to-end tests passing
- [ ] Extended the documentation
- [ ] Provided sample for the feature

[Mpdreamz]

Yes @adamsitnik this LGTM.

cc @flobernd who's the maintainer for the new .net client.

[Alirexaa]

The new UseElasticCloud method supports health check for elastic cloud. it should close: #2242

[Alirexaa]

@adamsitnik, we should block this PR until .NET 9 release, Right?

[adamsitnik]

we should block this PR until .NET 9 release, Right?

AFAIK the package won't be released to nuget.org until @unaizorrilla triggers some automation, so there is no need to wait with the merge.