feat: Handle provisioned concurrency and proactive initialization

[astuyve]

What does this PR do?

This PR won't take the first request to a new sandbox as a coldstart if it is greater than 10 seconds old. This is not exhaustive, but indicative of provisioned concurrency.

Motivation

Testing Guidelines

Additional Notes

Types of Changes

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

Check all that apply

• 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)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

[codecov-commenter]

Codecov Report

Merging #389 (8adc1ca) into main (0548d77) will decrease coverage by 0.16%.
The diff coverage is 74.07%.

❗ Current head 8adc1ca differs from pull request most recent head 9bd07e6. Consider uploading reports for the commit 9bd07e6 to get more accurate results

@@            Coverage Diff             @@
##             main     #389      +/-   ##
==========================================
- Coverage   80.84%   80.69%   -0.16%     
==========================================
  Files          38       38              
  Lines        1937     1953      +16     
  Branches      449      454       +5     
==========================================
+ Hits         1566     1576      +10     
- Misses        315      321       +6     
  Partials       56       56              

Impacted Files	Coverage Δ
src/trace/listener.ts	62.40% <16.66%> (-2.07%)	⬇️
src/utils/cold-start.ts	91.30% <87.50%> (-8.70%)	⬇️
src/index.ts	88.23% <100.00%> (+0.07%)	⬆️
src/metrics/enhanced-metrics.ts	91.89% <100.00%> (ø)
src/utils/index.ts	100.00% <100.00%> (ø)

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[maxday]

LGTM, love the tests