Added TimeoutPoller to have one thread for timers

[shayaantx]

As discussed in other pr, modified the TimeoutTimer to not be a unlimited thread pool, instead its one thread that lets TDS commands register/deregister with it, when a timeout is configured, and that thread will timeout the command if necessary. Included test cases.

Updated to include bulk copy functionality.

I literally formatted every single piece of code I touched, it seems much of IO buffer doesn't match the linked formatter, https://github.com/Microsoft/mssql-jdbc/blob/dev/mssql-jdbc_formatter.xml

[codecov-io]

Codecov Report

Merging #842 into dev will decrease coverage by 0.29%.
The diff coverage is 85.33%.

@@             Coverage Diff             @@
##                dev     #842     +/-   ##
===========================================
- Coverage     48.98%   48.68%   -0.3%     
+ Complexity     2821     2813      -8     
===========================================
  Files           116      118      +2     
  Lines         27877    27863     -14     
  Branches       4650     4637     -13     
===========================================
- Hits          13655    13566     -89     
+ Misses        12104    12101      -3     
- Partials       2118     2196     +78

Flag	Coverage Δ	Complexity Δ
#JDBC42	48.1% <85.33%> (-0.09%)	2759 <14> (+9)
#JDBC43	48.66% <85.33%> (-0.26%)	2813 <14> (-3)

Impacted Files	Coverage Δ	Complexity Δ
...a/com/microsoft/sqlserver/jdbc/TimeoutCommand.java	100% <100%> (ø)	5 <5> (?)
...in/java/com/microsoft/sqlserver/jdbc/IOBuffer.java	55.74% <77.77%> (-2.51%)	0 <0> (ø)
...va/com/microsoft/sqlserver/jdbc/TimeoutPoller.java	83.78% <83.78%> (ø)	9 <9> (?)
...om/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java	52.46% <90%> (-0.27%)	263 <0> (ø)
...m/microsoft/sqlserver/jdbc/SQLServerException.java	77.44% <0%> (-1.51%)	31% <0%> (-2%)
...om/microsoft/sqlserver/jdbc/ReaderInputStream.java	43.95% <0%> (-1.1%)	15% <0%> (ø)
...c/main/java/com/microsoft/sqlserver/jdbc/Util.java	60.99% <0%> (-1.08%)	89% <0%> (-4%)
...n/java/com/microsoft/sqlserver/jdbc/tdsparser.java	68.1% <0%> (-0.87%)	0% <0%> (ø)
...ncurrentlinkedhashmap/ConcurrentLinkedHashMap.java	38.14% <0%> (-0.65%)	42% <0%> (-1%)
... and 7 more

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[shayaantx]

@ulvii @cheenamalhotra

[shayaantx]

ok sorry, now the formatting should be correct, eclipse kept reverting the formatter I was using on my vm.....

[ulvii]

Please add the license header to the new files.

 /*
  * Microsoft JDBC Driver for SQL Server Copyright(c) Microsoft Corporation All rights reserved. This program is made
  * available under the terms of the MIT License. See the LICENSE file in the project root for more information.
  */

[shayaantx]

@ulvii anything other changes required? please let me know

[shayaantx]

@ulvii @cheenamalhotra anything I missed?

[ulvii]

Hi @shayaantx ,
The review is mostly done and we are targeting to merge the PR for the next preview release. Please stay tuned, as there might still be review comments depending on the results of internal testing.
Thank you for patience.

[shayaantx]

@ulvii no problem, just let me know, thanks

[peterbae]

Other than that one comment I made, this PR looks good to me.