fix(node-http-handler): throw TimeoutError for Node.js timeouts

[trivikr]

Issue #, if available:
Fixes: #1196

Description of changes:
This PR throws TimeoutError for Node.js timeouts ("ECONNRESET", "EPIPE", "ETIMEDOUT"), so that retryMiddleware can retry them.

• Tested with repro code given in ECONNRESET exceptions when running in Lambda environment #1196 (comment)
• The node-http-handler tests are being refactored in https://github.com/trivikr/aws-sdk-js-v3/tree/node-http-handler-tests and the test for this PR would be added later. This PR is posted to ensure fix is pushed in rc.7 release on 11/19.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-io]

Codecov Report

Merging #1693 (3b0d3d0) into master (de75f7e) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1693      +/-   ##
==========================================
- Coverage   79.77%   79.70%   -0.08%     
==========================================
  Files         325      329       +4     
  Lines       12087    12576     +489     
  Branches     2553     2671     +118     
==========================================
+ Hits         9643    10024     +381     
- Misses       2444     2552     +108     

Impacted Files	Coverage Δ
...tocol_tests/aws-restxml/commands/XmlMapsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ocol_tests/aws-restxml/commands/XmlBlobsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ocol_tests/aws-restxml/commands/XmlEnumsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ocol_tests/aws-restxml/commands/XmlListsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...col_tests/aws-restjson/commands/JsonMapsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ol_tests/aws-restjson/commands/JsonBlobsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ol_tests/aws-restjson/commands/JsonEnumsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ol_tests/aws-restjson/commands/JsonListsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...tests/aws-restxml/commands/XmlAttributesCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...tests/aws-restxml/commands/XmlNamespacesCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
... and 106 more

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[alexforsyth]

LGTM, minor comment

[github-actions]

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