Remove base db struct

[Eittipat]

Description

Remove base db

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (changes that do NOT affect functionality)
• Adds or updates testing
• This change requires a documentation update

[codecov]

Codecov Report

❌ Patch coverage is 89.93289% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
db/code_db.go	86.36%	6 Missing and 3 partials ⚠️
db/destroyed_account_db.go	92.00%	4 Missing and 2 partials ⚠️

Files with missing lines	Coverage Δ
db/exception_db.go	82.45% <100.00%> (ø)
db/substate_db.go	96.06% <100.00%> (ø)
db/update_db.go	86.88% <100.00%> (-5.74%)	⬇️
db/destroyed_account_db.go	92.18% <92.00%> (-0.38%)	⬇️
db/code_db.go	93.12% <86.36%> (-6.88%)	⬇️

... and 2 files with indirect coverage changes

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