[exporter/elasticsearch] Workaround TSDB array dimension limitation f…

…or metrics OTel mode (open-telemetry#35009)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
Elasticsearch TSDB does not support array dimensions. Workaround it by
stringifying attribute array values in OTel mapping mode for metrics.

Refactor to improve test code reuse.

**Link to tracking Issue:** <Issue number if applicable>

Fixes open-telemetry#35004

**Testing:** <Describe what testing was performed and which tests were
added.>

Added exporter test for otel mode logs, metrics and traces

**Documentation:** <Describe the documentation added.>

.chloggen/elasticsearchexporter_workaround-tsdb-array-dimension.yaml

@@ -0,0 +1,28 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: elasticsearchexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Stringify attribute array values in metrics OTel mode
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [35004]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+  Elasticsearch TSDB does not support array dimensions.
+  Workaround it by stringifying attribute array values in OTel mapping mode for metrics.
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]