Ensure input packages with `otelcol` input type (e.g. "OTel integrations") can be built, tested, and published with `elastic-package`

[kpollich]

The new OTel integrations input package type introduced in elastic/package-spec#906 should be fully supported in elastic-package. Integration authors should be able to build, test, and publish new versions of their OTel integrations.

A detail to take into account is that data streams have an additional otel suffix, see elastic/kibana#232628.

[mrodm]

Created PR to add support for input packages containing the new otelcol input type with policy tests: #2873

Pending to review the status of system tests.

[mrodm]

After doing some tests with the current status of these PRs:

• Complete OTel configuration pipelines with an exporter kibana#233090
• Prepare OTel Elasticsearch exporter with the credentials of the output fleet-server#5469

It is required to update how policy tests are validated in case of the otelcol input. Working on that #2886

Draft PR to add support to run system tests on input packages defining an otelcol input: #2885

[mrodm]

Tested other commands a part from elastic-package test, and they also worked successfully using the test httpcheck package:

• elastic-package install -v
• elastic-package uninstall -v
• elastic-package build -v
• elastic-package check -v
• elastic-package lint -v
• elastic-package format -v

[mrodm]

Working on this PR to add support for system tests #2885
But tests are failing because there is no Index Template created:

[0] failed to load mappings from index template preview (metrics-httpcheck.check.otel): error getting mapping: [400 Bad Request] {"error":{"root_cause":[{"type":"illegal_argument_exception","reason":"unable to simulate template [metrics-httpcheck.check.otel] that does not exist"}],"type":"illegal_argument_exception","reason":"unable to simulate template [metrics-httpcheck.check.otel] that does not exist"},"status":400}