fix(lambda-at-edge): fix dynamic route precedence conflicting with fallback pages

[dphang]

Fixes: #646

• Before fallback page is returned, we need to check for non-dynamic and dynamic routes that match it that may not be fallback.
• Non-dynamic routes are already checked; this PR adds checking for dynamic routes as well.

A bit strange to mix this with static fallback logic, but the issue is fallback is checked early in the routing logic before any non-dynamic or dynamic routes, hence we need to check this as part of it. Will revisit this and do a cleaner refactor once we decouple Lambda@Edge and core routing logic.

Tests

Added some end-to-end tests to verify this behavior.

[codecov]

Codecov Report

Merging #714 into master will increase coverage by 0.03%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master     #714      +/-   ##
==========================================
+ Coverage   79.79%   79.83%   +0.03%     
==========================================
  Files          55       55              
  Lines        1747     1765      +18     
  Branches      373      378       +5     
==========================================
+ Hits         1394     1409      +15     
- Misses        295      298       +3     
  Partials       58       58              

Impacted Files	Coverage Δ
...ackages/libs/lambda-at-edge/src/default-handler.ts	94.46% <83.33%> (-0.86%)	⬇️

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