Updated dbname and service name for both query sample and top query log events

[sjyothi54]

Description

This PR fixes a bug in how the oracledbreceiver collecting db.namespace for query_sample
The Problem:
Previously, the code used the Oracle service_name (the network connection string) as the db.name. This was incorrect for modern multi-tenant (CDB/PDB) Oracle setups. If one database used 3 different connection services, the collector treated them as 3 completely separate databases, splitting up your performance data and cluttering dashboards.

The Fix:

• Moved the service_name to the correct OpenTelemetry attribute (db.namespace).
• Added a JOIN to v$containers using the container ID (con_id). This ensures that db.name always shows the actual name of the Pluggable Database (PDB)
• Used NVL (null handling) so that if a system background task doesn't have a PDB name, it defaults cleanly to a placeholder string rather than sending a blank space which breaks dashboards.

Link to tracking issue

Fixes
#48996

Testing

• Added unit tests in scraper_test.go
• Updated expectedSamplesFile.yaml and exepectedQueryTextAndPlanQuery.yaml in testdata

Documentation

Updated documentation.md with the new db.namespace and db.servicename for top and query sample log events

Authorship

• I, a human, wrote this pull request description myself.

[crobert-1]

Suggested change

	stringValue: ORCLPDB1
	stringValue: ORCL

Probably not a big deal, but it looks like this should just be the service, not the db name.

[crobert-1]

These should be removed unless they're different from before.

[crobert-1]

I think we should remove this sentence, we don't need to recommend how to handle this outside the scope of the collector itself.