[Starfish] Add db attributes to database span's span data

[AbhiPrasad]

To get an overview of this work across all SDKs, please visit:
https://github.com/orgs/getsentry/projects/135

Parent issue: getsentry/team-sdks#19

For the starfish db module it was determined that we need extra database attributes.

db.name should be set if possible, but is not required. db.system should match the list in OpenTelemetry's well known conventions.

Attribute	Type	Description	Examples	Requirement Level
db.system	string	An identifier for the database management system (DBMS) product being used.	sqlite	Required
db.name	string	This attribute is used to report the name of the database being accessed. For commands that switch the database, this should be set to the target database (even if the command fails).	customers; main	Conditionally Required: If applicable.

These values should be set on span.data.

Motivation

This is being done for the Sentry's new performance views for databases. See a WIP example of the view below:

[buenaflor]

Should these attributes also be set on spans for opening/closing db? or strictly only for queries

[AbhiPrasad]

@buenaflor preferably only on the query span, but it's also fine to duplicate the attributes among all db related spans.