feat: Validate records against stream schema in standard tap tests

[edgarrmondragon]

Failure example:

FAILED tests/external/test_tap_gitlab.py::TestSampleTapGitlab::test_tap_stream_record_matches_stream_schema[epic_issues] - AssertionError: Record does not match stream schema: '2021-11-03T15:21:07.350Z' is not of type 'null' (path: closed_at)
'flow::Review' is not of type 'object' (path: labels.0)
'kind::Feature' is not of type 'object' (path: labels.1)
'valuestream::Hub' is not of type 'object' (path: labels.2)
'2021-11-05' is not of type 'null' (path: milestone.due_date)
'2021-10-30' is not of type 'null' (path: milestone.start_date)
'project_id' is a required property (path: milestone)
FAILED tests/external/test_tap_gitlab.py::TestSampleTapGitlab::test_tap_stream_record_matches_stream_schema[issues] - AssertionError: Record does not match stream schema: {'id': 1134865, 'username': 'edgarrmondragon', 'name': 'Edgar R. Mondragón', 'state': 'active', 'avatar_url': 'https://gitlab.com/uploads/-/system/user/avatar/1134865/avatar.png', 'web_url': 'https://gitlab.com/edgarrmondragon'} is not of type 'integer' (path: assignees.0)

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📚 Documentation preview 📚: https://meltano-sdk--1711.org.readthedocs.build/en/1711/

[codecov]

Codecov Report

Merging #1711 (91818f1) into main (8b76d8a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

❗ Current head 91818f1 differs from pull request most recent head 9e2dd94. Consider uploading reports for the commit 9e2dd94 to get more accurate results

@@            Coverage Diff             @@
##             main    #1711      +/-   ##
==========================================
+ Coverage   85.08%   85.11%   +0.03%     
==========================================
  Files          59       59              
  Lines        4868     4878      +10     
  Branches      807      809       +2     
==========================================
+ Hits         4142     4152      +10     
  Misses        527      527              
  Partials      199      199              

Impacted Files	Coverage Δ
singer_sdk/testing/suites.py	100.00% <ø> (ø)
singer_sdk/testing/tap_tests.py	83.73% <100.00%> (+1.43%)	⬆️

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