Clear returnStatus between two queries on the same connection

[tc-hib]

Fixes #654.

• Add a new test to demonstrate that returnStatus is not cleared at all between two queries on the same connection.
• Move returnStatus to the same place as outs since they have the same scope, and a very similar usage.
• Gather returnStatus and outs into a struct, because we have to pass both to several functions, and also because I plan to propose a third member. outs becomes outs.params.
• Ensure outs is cleared even when we get an early error.

[codecov[bot]]

Codecov Report

Merging #675 (165a70f) into master (a78da2a) will increase coverage by 0.07%. The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master     #675      +/-   ##
==========================================
+ Coverage   70.19%   70.26%   +0.07%     
==========================================
  Files          23       23              
  Lines        5163     5173      +10     
==========================================
+ Hits         3624     3635      +11     
  Misses       1310     1310              
+ Partials      229      228       -1     

Impacted Files	Coverage Δ
mssql.go	87.04% <80.00%> (-0.23%)	:arrow_down:
bulkcopy.go	57.20% <100.00%> (ø)
mssql_go19.go	95.74% <100.00%> (ø)
tds.go	65.59% <100.00%> (-0.17%)	:arrow_down:
token.go	61.23% <100.00%> (+0.75%)	:arrow_up:

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