Added warning message to fetch_table, added fetch_table_bkchin()

[cbedwards-dfw]

Address #48

BackwardsFRAM table in chinook databases has a stock_id field that uses a different numbering system than the stock_id field in all other chinook tables.

This means that, for example joining fetch_table(fram.db, table_name = "BackwardsFRAM") and fetch_table(fram.db, table_name = "Cohort") will silently produce a meaningless result when working with a Chinook database.

To prevent this, this branch

1. Adds a CLI warning specifically when fetching the BackwardsFRAM table from a Chinook database. Warning behavior can be toggled with new optional warn argument.
2. adds fetch_table_bkchin(), which uses fetch_table() but then renames the problematic stock_id column to bk_stock_id, and then uses the chinook bkfram lookup table in {framrosetta} to add in a functional stock_id column and the names associated with the bkfram stocks.

Example comparison:

fram.db = connect_fram_db("2024 Pre-Season Chinook DB.mdb")
tab1 = fetch_table(fram.db, table_name = "BackwardsFRAM") |> 
  dplyr::left_join(fetch_table(fram.db, table_name = "Cohort"))
## tab1 has meaningless matching between the Cohort table and BackwardsFRAM table
## due to the non-synonymous stock_id column

tab2 = fetch_table_bkchin(fram.db)  |> 
  dplyr::left_join(fetch_table(fram.db, table_name = "Cohort"))
## tab2 has the correct matching

disconnect_fram_db(fram.db)