chore: Refactor OTel resources

[skhalash]

Description

Changes proposed in this pull request (what was done and why):

• The esources/otelcollector package previously defined a "generic" gateway/agent applier-deleter, which required external configuration. However, as gateways for different signal types (e.g., metrics and traces) diverged, the number of configuration parameters increased, leading to complexity.

This PR encapsulates the logic for handling different concrete gateways and agents, simplifying the usage of the package. Additionally, it lays the groundwork for easier integration of log agent support in the future.

Changes refer to particular issues, PRs or documents:

• chore: Refactor LogPipeline, MetricPipeline, and TracePipeline Controllers #1644

Traceability

• The PR is linked to a GitHub issue.
• The follow-up issues (if any) are linked in the Related Issues section.
• If the change is user-facing, the documentation has been adjusted.
• If a CRD is changed, the corresponding Busola ConfigMap has been adjusted.
• The feature is unit-tested.
• The feature is e2e-tested.