refactor: made unit tests use separate real dbs

[pompon0]

What ❔

Made unit tests use separate real dbs created in a temporary postgres container.

Why ❔

It makes the tests more realistic and greatly simplifies the dal crate.

[slowli]

DB tests look significantly nicer than before 👍

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (f048485) 35.63% compared to head (fd988a3) 35.88%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #213      +/-   ##
==========================================
+ Coverage   35.63%   35.88%   +0.25%     
==========================================
  Files         520      517       -3     
  Lines       28350    27627     -723     
==========================================
- Hits        10103     9915     -188     
+ Misses      18247    17712     -535     

Files	Coverage Δ
core/lib/dal/src/blocks_dal.rs	79.44% <ø> (+6.67%)	⬆️
core/lib/dal/src/blocks_web3_dal.rs	37.01% <ø> (+0.64%)	⬆️
core/lib/dal/src/connection/holder.rs	0.00% <ø> (ø)
core/lib/dal/src/events_dal.rs	100.00% <ø> (ø)
core/lib/dal/src/events_web3_dal.rs	37.77% <ø> (-2.23%)	⬇️
core/lib/dal/src/instrument.rs	56.06% <ø> (+0.83%)	⬆️
core/lib/dal/src/lib.rs	23.07% <ø> (-4.87%)	⬇️
core/lib/dal/src/storage_dal.rs	78.46% <ø> (-1.23%)	⬇️
core/lib/dal/src/storage_logs_dal.rs	79.75% <ø> (+0.74%)	⬆️
core/lib/dal/src/transactions_web3_dal.rs	57.14% <ø> (ø)
... and 6 more

... and 98 files with indirect coverage changes

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