Test: write tests for file backed db

[pedrocarlo]

First attempt at closing #1212. Also with this PR, I added the option of using with syntax for TestLimboShell. It automatically closes the shell on error, and facilitates error handling overall. If this is merged, I can update the other python tests to use with as well.

[pedrocarlo]

Tests already detected some problems with btree

[PThorpe92]

UPDATE also specifically overwrites the cell (usually), so it would be valuable to add some tests like:

sqlite3: create new update.db file with test table, 3 cols 1000 rows

limbo: open update.db, update 1 column in that table with values that are equal or smaller than the original value. Then update another column with a value that is larger.

sqlite3: open update.db and assert that all the columns have the expected counts/values

[pedrocarlo]

UPDATE also specifically overwrites the cell (usually), so it would be valuable to add some tests like:

sqlite3: create new update.db file with test table, 3 cols 1000 rows

limbo: open update.db, update 1 column in that table with values that are equal or smaller than the original value. Then update another column with a value that is larger.

sqlite3: open update.db and assert that all the columns have the expected counts/values

Oh that is good to test. I will add this. I'm also adding the UV workspace stuff to facilitate dependency management for our Python code.

[PThorpe92]

Great stuff here