Upgrade steep and make it a bit more strict

[marcotc]

Upgrade steep to 1.9.1 and rbs to 3.7.0, as I've encountered recent steep bugs that have been fixed in newer versions.

I also played a bit with the default type checking level: we currently use default but I've tried strict and noticed there are a few very helpful checks.
Most notably:

• DifferentMethodParameterKind which checks that your .rbs declarations actually match the method parameters.
• IncompatibleAssignment which checks if we are assigning incompatible types to fields we've explicitly typed already.

There's one functional change which steep caught in this upgrade: there was one dead code branch in lib/datadog/appsec/processor/rule_loader.rb, which I removed. This is actually dead code, since ip_passlist comes from a non-nillable configuration option.

Change log entry
None

[datadog-datadog-prod-us1]

Datadog Report

Branch report: bump-steep
Commit report: 611bcf2
Test service: dd-trace-rb

✅ 0 Failed, 22094 Passed, 1457 Skipped, 5m 16.97s Total Time

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.75%. Comparing base (65fb81d) to head (611bcf2).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4221   +/-   ##
=======================================
  Coverage   97.75%   97.75%           
=======================================
  Files        1355     1355           
  Lines       82165    82163    -2     
  Branches     4207     4207           
=======================================
- Hits        80321    80320    -1     
+ Misses       1844     1843    -1     

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[sarahchen6]

👍

[Strech]

I think my suggestions are non-blocking, but gems versions are kind-a important

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-12-13 19:08:38

Comparing candidate commit 611bcf2 in PR branch bump-steep with baseline commit 65fb81d in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.