Move database connection utils to dbconn

[asdine]

There currently are two separate connection helpers, using two different PG drivers.
This unifies database connection helpers and merges them into one single package.
dbconn is now the only package responsible for connecting to the database and database migrations.
dbutil is now only responsible for generic helpers.

Note: This relies on adding support for driver.ConnBeginTx on the sqlhooks package qustavo/sqlhooks#33

Fixes #16586

[sourcegraph-bot]

Notifying subscribers in CODENOTIFY files for diff f96e136...46ae581.

Notify	File(s)
@efritz	internal/db/basestore/handle.go internal/db/dbconn/dbconn.go internal/db/dbconn/migration.go internal/db/dbtest/dbtest.go internal/db/dbtesting/dbtesting.go internal/db/dbutil/dbutil.go
@keegancsmith	cmd/gitserver/main.go

[ryanslade]

LGTM. Did you check a migration just to be sure that nothing broke there?

[asdine]

@ryanslade Not yet, once sqlhooks gets updated I will run integration tests and a migration to check if every is fine

[tsenart]

We can merge this if we use your fork as a dependency and update later once it's merged upstream.

[codecov]

Codecov Report

Merging #17399 (46ae581) into main (f96e136) will increase coverage by 0.01%.
The diff coverage is 14.54%.

@@            Coverage Diff             @@
##             main   #17399      +/-   ##
==========================================
+ Coverage   51.87%   51.89%   +0.01%     
==========================================
  Files        1716     1717       +1     
  Lines       85296    85275      -21     
  Branches     7647     7634      -13     
==========================================
+ Hits        44246    44251       +5     
+ Misses      37148    37124      -24     
+ Partials     3902     3900       -2     

Flag	Coverage Δ
go	50.87% <14.54%> (+0.02%)	⬆️
integration	30.69% <ø> (+<0.01%)	⬆️
storybook	30.34% <ø> (ø)
typescript	54.35% <ø> (+<0.01%)	⬆️
unit	34.72% <ø> (ø)

Impacted Files	Coverage Δ
cmd/gitserver/main.go	10.12% <0.00%> (ø)
internal/db/basestore/handle.go	61.53% <0.00%> (ø)
internal/db/dbconn/dbconn.go	11.38% <0.00%> (ø)
internal/db/dbutil/dbutil.go	19.14% <ø> (+2.32%)	⬆️
internal/db/dbconn/migration.go	17.39% <17.39%> (ø)
client/web/src/nav/StatusMessagesNavItem.tsx	87.71% <0.00%> (+1.75%)	⬆️
.../internal/codeintel/resolvers/graphql/locations.go	85.56% <0.00%> (+4.12%)	⬆️