docs(tutorial): fix broken internal links

[heitorlessa]

Issue #, if available:

Description of changes:

All links pointing to other internal sections (e.g. Tracer, Logger) and their respective sections were broken.

We also update Event Handler example (ApiGatewayResolver) to use the new specialized one APIGatewayRestResolver to give customers a first class experience on autocompleting available properties.

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

Breaking change checklist

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

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View rendered docs/tutorial/index.md

[codecov-commenter]

Codecov Report

Merging #1000 (ea611a1) into develop (168ec48) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #1000   +/-   ##
========================================
  Coverage    99.96%   99.96%           
========================================
  Files          119      119           
  Lines         5347     5347           
  Branches       610      610           
========================================
  Hits          5345     5345           
  Partials         2        2           

Impacted Files	Coverage Δ
aws_lambda_powertools/event_handler/__init__.py	100.00% <100.00%> (ø)

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[heitorlessa]

Also discovered we accidentally slipped the top level imports for event handler while running through the tutorial.

Initially added here: #978

Adding the fix as part of this PR too.