[SERF-3424] Fix DB connection initialization for test environment

[Neurostep]

Description

During the Go Chassis and Go SDK upgrades in the document-search service, we noticed a broken behavior of the database.NewConnection function when called in the test environment: the following error was raised

 search_test.go:59: 
                Error Trace:    /app/pkg/search/search_test.go:59
                                                        /app/pkg/search/search_test.go:182
                Error:          Expected nil, but got: &errors.errorString{s:"invalid DSN: missing the slash separating the database name"}
                Test:           TestSearchHandlerHasTimeout
--- FAIL: TestSearchHandlerHasTimeout (0.00s)

The issue is due to the fact that we started using sqltrace from the dd-trace-go library to register the driver and initialize the DB connection, but the test-related initialization was still relying on the sql interface from the database/sql package.

In this PR we upgraded the go-txdb to the latest v0.1.9 version and used sqltrace for all environments.

Testing considerations

• Deploy service with DB connection in the development and/or staging environment and check if all works as expected

Checklist

• Prefixed the PR title with the JIRA ticket code
• Performed simple, atomic commits with good commit messages
• Verified that the commit history is linear and commits are squashed as necessary
• Thoroughly tested the changes in development and/or staging
• Updated the README.md as necessary

Related links

• https://github.com/scribd/document-search/pull/76
• [SERF-3423] Adding MySQL driver instrumentation #112
• SERF-3424

[laynax]

LGTM

[laynax]

LGTM