tidy up dependencies

[jangorecki]

PR includes following changes:

• move DBI from Depends to Imports in DCF:
  It is good practice to avoid Depends when possible in favor of Imports. Side effect is that we need to explicitly load DBI namespace if we want to use functions from it in examples
• utils removed from DCF:
  No need to specify it. It is enough if it is in NAMESPACE
• removed importFrom DBI in NAMESPACE:
  DBI was imported completely already in NAMESPACE so this line is redundant
• test script correctly escapes suggested package:
  as per recommendation in WRE "...recommendation to use suggested packages conditionally in tests does also apply to packages used to manage test suites: a notorious example was testthat..."

[krlmlr]

Thanks. Good catch on the @importFrom, I'll cherry-pick that.

The other points are valid, but also not very relevant. Shelving them for now.

[codecov-commenter]

Codecov Report

Merging #21 (42ea471) into main (cc4f7cb) will not change coverage.
Report is 2 commits behind head on main.
The diff coverage is n/a.

❗ Current head 42ea471 differs from pull request most recent head 61d7273. Consider uploading reports for the commit 61d7273 to get more accurate results

@@           Coverage Diff           @@
##             main      #21   +/-   ##
=======================================
  Coverage   85.63%   85.63%           
=======================================
  Files         106      106           
  Lines        3598     3598           
=======================================
  Hits         3081     3081           
  Misses        517      517           

Files	Coverage Δ
R/csv.R	79.48% <ø> (ø)
R/dbConnect__duckdb_driver.R	100.00% <ø> (ø)
R/dbIsValid__duckdb_driver.R	100.00% <ø> (ø)
R/register.R	91.89% <ø> (ø)

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