fix: keep the sre_constants module [backport #6255 to 1.14]

[P403n1x87]

Backport of #6255 to 1.14

The re module imports from the sre_constants module at runtime. This might cause issues when modules are unloaded in the sitecustomize.

Fixes #6197.

Checklist

• Change(s) are motivated and described in the PR description.
• Testing strategy is described if automated tests are not included in the PR.
• Risk is outlined (performance impact, potential for breakage, maintainability, etc).
• Change is maintainable (easy to change, telemetry, documentation).
• Library release note guidelines are followed. If no release note is required, add label changelog/no-changelog.
• Documentation is included (in-code, generated user docs, public corp docs).
• Backport labels are set (if applicable)

Reviewer Checklist

• Title is accurate.
• No unnecessary changes are introduced.
• Description motivates each change.
• Avoids breaking API changes unless absolutely necessary.
• Testing strategy adequately addresses listed risk(s).
• Change is maintainable (easy to change, telemetry, documentation).
• Release note makes sense to a user of the library.
• Reviewer has explicitly acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment.
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[pr-commenter]

Benchmarks

Comparing candidate commit e631ad7 in PR branch backport-6255-to-1.14 with baseline commit 84d8893 in branch 1.14.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 93 cases.

scenario:flasksimple-tracer-and-profiler

• 🟥 execution_time [+0.371ms; +0.486ms] or [+6.040%; +7.914%]