add 1.19 to the unit test matrix

[bmoffatt]

Description of changes:

https://go.dev/doc/devel/release#go1.19 released 8/2, should be running tests with it

posting this CR also showed that the listing workflow rotted when latest go became 1.19, so

• bumped the linter version
• did a gofmt -s -w **/*.go to appease the new formatter
• and suppressed the recommendations about the "io/ioutil" rename, since I'm not emotionally ready tonight to drop build support for versions less than go1.16 :)

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

[codecov-commenter]

Codecov Report

Merging #462 (69f2b2a) into main (13ee405) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #462   +/-   ##
=======================================
  Coverage   69.69%   69.69%           
=======================================
  Files          20       20           
  Lines        1201     1201           
=======================================
  Hits          837      837           
  Misses        297      297           
  Partials       67       67           

Impacted Files	Coverage Δ
cfn/response.go	69.44% <ø> (ø)
cfn/wrap.go	66.66% <ø> (ø)
cmd/build-lambda-zip/main.go	34.66% <ø> (ø)
events/codebuild.go	40.90% <ø> (ø)
lambda/entry.go	81.81% <ø> (ø)
lambda/extensions_api_client.go	0.00% <ø> (ø)
lambda/handler.go	92.08% <ø> (ø)
lambda/runtime_api_client.go	73.13% <ø> (ø)

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[carlzogh]

LGTM! 🚀