Update AWS dependencies, remove vendor folder

[nhinsch]

What does this PR do?

• Update dependencies:
  • github.com/aws/aws-lambda-go v1.11.1 -> v1.25.0
  • github.com/aws/aws-sdk-go v1.36.29 -> v1.40.2
  • github.com/aws/aws-xray-sdk-go v1.0.0-rc.9 -> v1.6.0
• Remove the vendor directory that contained copies of dependencies. I am not sure if this directory was actually being used, as it was missing the vendor/modules.txt manifest file. Either way, we don't really need to vendor our dependencies for this library; we can build by directly downloading dependencies from their sources like we do for our other libraries.

Motivation

A community PR pointed out the need to upgrade github.com/aws/aws-xray-sdk-go. I decided to use this opportunity to update some other dependencies and clean up the vendor directory as well.

Testing Guidelines

Unit and integration tests.

Types of changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [x] Misc (docs, refactoring, dependency upgrade, etc.)

Checklist

• [x] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [x] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog

[codecov-commenter]

Codecov Report

Merging #84 (078c074) into main (a0a402d) will increase coverage by 0.71%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
+ Coverage   82.45%   83.17%   +0.71%     
==========================================
  Files          12       12              
  Lines         644      725      +81     
==========================================
+ Hits          531      603      +72     
- Misses         89       98       +9     
  Partials       24       24              

Impacted Files	Coverage Δ
ddlambda.go	78.04% <0.00%> (-2.24%)	:arrow_down:
internal/trace/listener.go	59.32% <0.00%> (-1.79%)	:arrow_down:
internal/metrics/kms_decrypter.go	76.00% <0.00%> (-1.28%)	:arrow_down:
internal/metrics/time.go	66.66% <0.00%> (ø)
internal/metrics/batcher.go	100.00% <0.00%> (ø)
internal/metrics/context.go	100.00% <0.00%> (ø)
internal/wrapper/wrap_handler.go	100.00% <0.00%> (ø)
internal/metrics/listener.go	75.53% <0.00%> (+1.12%)	:arrow_up:
internal/metrics/api.go	90.00% <0.00%> (+1.32%)	:arrow_up:
internal/trace/context.go	76.56% <0.00%> (+1.56%)	:arrow_up:
... and 2 more

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