Add db.Exec and db.Prepare to the sql rule

[kaiili]

Problem

fixes #756

Details :

can be seen in #756.
G201,G202 only match Query, QueryContext, QueryRow, QueryRowContext .
If there is a SQLStr like the following, there will be problems with matching.

db.Exec("SELECT " + cols + " FROM DUAL")

Solution

Add Exec, ExecContext, Prepare and PrepareContext.

[codecov-commenter]

Codecov Report

Merging #763 (407051f) into master (7be6d4e) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #763      +/-   ##
==========================================
+ Coverage   73.72%   73.82%   +0.10%     
==========================================
  Files          47       47              
  Lines        2953     2953              
==========================================
+ Hits         2177     2180       +3     
+ Misses        712      710       -2     
+ Partials       64       63       -1     

Impacted Files	Coverage Δ
rules/sql.go	79.39% <100.00%> (+1.50%)	⬆️

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