Feature/add core functions

[github-actions[bot]]

Docker image from this PR (e088e5bf01d1751db71cc32549c17dfd6839634b) created

docker pull ghcr.io/rmi-pacta/workflow.factset:pr1

[AlexAxthelm]

This PR largely captures the current state of https://github.com/RMI-PACTA/pacta.data.preparation/tree/main/data in its current state, with some minor changes to improve overall flow, logging and respond to linting/style.

Key changes:

• creating of export_pacta_files() function (with sensible defaults) which wraps the other functions in a simple interface
• externalizing the database connection from individual get_* functions
• simplification of function and variable names
• lintr and hadolint checks
• remove keychain and rstudio prompts form DB connection function

cc @cjyetman