Add typing for Base64, TagBuilder, and Workers::Polling#stop

[marcotc]

What does this PR do?

Small type improvements:

• Utils::Base64: :: prefixes added to all String types; strict_decode64 arg typed as ::String (return remains untyped — unpack1 return type is format-dependent and Steep can't narrow it)
• TagBuilder: :: prefixes on all types; tags() accepts any settings (DSL settings object is intentionally open)
• Workers::Polling#stop: untyped → bool (always returns true/false from join/terminate)

How to test the change?

bundle exec steep check \
  lib/datadog/core/utils/base64.rb \
  lib/datadog/core/tag_builder.rb \
  lib/datadog/core/workers/polling.rb

Changelog

None.

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-03-13 21:02:42

Comparing candidate commit 3e1d1b0 in PR branch marcotc/type-core-misc-utils with baseline commit 6b340a0 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 46 metrics, 0 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'