Support for reading data source from file

[OskarsPakers]

Description

Fixes #428

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

1. Created a local file dsn.txt with content "oracle://username:password@host:1521/instance"
2. Executed go run main.go --database.dsnFile=./dsn.txt
3. Opened http://localhost:9161/metrics and verified oracledb_tablespace_bytes metrics are present

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• [] I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Updated version in Makefile respecting semver v2