LSIF: extract common DB columns into lsif_dumps table

Created by: chrismwendt

Impact This is purely a refactor of DB tables in preparation for multi-lang/project support. There's no real logic or behavior being changed here.

Motivation Multi-lang/project support will require a set of wildcards to be associated with each LSIF dump, and doing so on the DB schema prior to this PR would result in a wildcards column attached to a few different tables, resulting in duplication of data and an increased chance of bugs. After this PR, we'll only need to add the new column wildcards to one table.

Implementation

• Factors out the repository and commit columns from a few tables and puts them into a dedicated lsif_dumps table
• Drops the lsif_data_markers table (superseded by lsif_dumps)

See the RFC discussion

Test plan: manually tried it on https://github.com/chrismwendt/cross-app and https://github.com/chrismwendt/cross-lib