feat(scopes): extract transaction sampling logic into TransactionSampler

[Litarnus]

No description provided.

[sentry]

Bug: The strict comparison $sampleRate === 0.0 fails when the sample rate is an integer 0. The code works by accident, but the explicit check for a zero sample rate is bypassed.
_{Severity: LOW}

Suggested Fix

Change the strict comparison === 0.0 to a non-strict comparison == 0 or cast the sample rate to a float before the comparison, like (float) $sampleRate === 0.0. This will correctly handle both integer 0 and float 0.0 values, aligning the code with its intended behavior. Apply this fix at both line 83 and line 151.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: src/Tracing/TransactionSampler.php#L83

Potential issue: The code checks if the sample rate is zero using a strict comparison,
`if ($sampleRate === 0.0)`. However, the configuration for `traces_sample_rate` allows
an integer value. If a user configures the sample rate as integer `0`, the strict
comparison `0 === 0.0` will evaluate to `false`. This causes the intended early return
to be skipped. While the subsequent logic currently leads to the correct outcome of not
sampling the transaction, it does so accidentally because the condition `$sampleRand <
0` is always false. This makes the code fragile and reliant on an implementation detail
that could change in the future, breaking the zero-sampling behavior. A similar issue
exists in the `sampleRate()` method.

Also affects:

• src/Tracing/TransactionSampler.php:151

_{Did we get this right? 👍 / 👎 to inform future reviews.}