Remove hardcoded error messages from test file

[peterbae]

Self-explanatory. Moved some error messages to the TestResources file.

[codecov-io]

Codecov Report

Merging #904 into dev will decrease coverage by 0.11%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev     #904      +/-   ##
============================================
- Coverage     48.79%   48.67%   -0.12%     
+ Complexity     2824     2814      -10     
============================================
  Files           118      118              
  Lines         27877    27877              
  Branches       4642     4642              
============================================
- Hits          13602    13569      -33     
- Misses        12086    12117      +31     
- Partials       2189     2191       +2

Flag	Coverage Δ	Complexity Δ
#JDBC42	48.2% <ø> (-0.14%)	2772 <ø> (-11)
#JDBC43	48.57% <ø> (-0.12%)	2809 <ø> (-9)

Impacted Files	Coverage Δ	Complexity Δ
...om/microsoft/sqlserver/jdbc/ReaderInputStream.java	45.05% <0%> (-2.2%)	15% <0%> (ø)
...rc/main/java/com/microsoft/sqlserver/jdbc/DDC.java	45.33% <0%> (-1.09%)	109% <0%> (-1%)
...m/microsoft/sqlserver/jdbc/SQLServerResultSet.java	32.43% <0%> (-0.66%)	253% <0%> (-7%)
...c/main/java/com/microsoft/sqlserver/jdbc/Util.java	60.99% <0%> (-0.44%)	89% <0%> (-1%)
...n/java/com/microsoft/sqlserver/jdbc/Parameter.java	64.12% <0%> (-0.21%)	64% <0%> (ø)
...om/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java	52.52% <0%> (-0.13%)	265% <0%> (-1%)
...in/java/com/microsoft/sqlserver/jdbc/IOBuffer.java	55.89% <0%> (-0.1%)	0% <0%> (ø)
...rc/main/java/com/microsoft/sqlserver/jdbc/dtv.java	62.63% <0%> (-0.06%)	0% <0%> (ø)

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