fix(connection): improve connection management

[danielebriggi]

• resolve the creation of two connections. The dynamic import of the connection modules delayed the initialization of the SQLiteCloudConnection object. Between the initialization of the Database object and the call to sql() method, the connection was not yet initialized
• connection to the database and the commands are put in queue to ensure the connection to be ready (the socket connection is a background operation)
• remove the implicit connection to the database in the sql() methods. We want the user be aware of the status of the connection (eg, due to open transactions)
• enable TCP keep alive to be notified of the most of the cases of errors on the TCP socket

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 76.06838% with 28 lines in your changes missing coverage. Please review.

Project coverage is 86.33%. Comparing base (717b862) to head (12c129f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/drivers/database.ts	76.84%	22 Missing ⚠️
src/drivers/connection-ws.ts	69.23%	4 Missing ⚠️
src/drivers/connection-tls.ts	71.42%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #219      +/-   ##
==========================================
- Coverage   87.28%   86.33%   -0.96%     
==========================================
  Files          11       11              
  Lines         975      973       -2     
  Branches      287      288       +1     
==========================================
- Hits          851      840      -11     
- Misses        124      133       +9     

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[danielebriggi]

ref: sqlitecloud/docs#111

[Gioee]

generally lgtm, the only important thing remained to do is to update examples