feat: collect user agent in normalized span tag `http.useragent`

[avara1986]

Description

Collect user agent in normalized span tag http.useragent

Checklist

• [x] Title must conform to conventional commit.
• [x] Add additional sections for feat and fix pull requests.
• [x] Ensure tests are passing for affected code.

Reviewer Checklist

• [ ] Title is accurate.
• [ ] Description motivates each change.
• [ ] No unnecessary changes were introduced in this PR.
• [ ] PR cannot be broken up into smaller PRs.
• [ ] Avoid breaking API changes unless absolutely necessary.
• [ ] Tests provided or description of manual testing performed is included in the code or PR.
• [ ] Release note has been added for fixes and features, or else changelog/no-changelog label added.
• [ ] All relevant GitHub issues are correctly linked.
• [ ] Backports are identified and tagged with Mergifyio.
• [ ] Add to milestone.

[codecov-commenter]

Codecov Report

Merging #3987 (561a28d) into 1.x (e8be033) will increase coverage by 0.00%. The diff coverage is 81.30%.

@@           Coverage Diff           @@
##              1.x    #3987   +/-   ##
=======================================
  Coverage   78.90%   78.91%           
=======================================
  Files         720      720           
  Lines       57255    57328   +73     
=======================================
+ Hits        45179    45240   +61     
- Misses      12076    12088   +12     

Impacted Files	Coverage Δ
tests/contrib/flask/test_flask_appsec.py	0.00% <0.00%> (ø)
tests/contrib/flask/test_flask_snapshot.py	0.00% <0.00%> (ø)
tests/contrib/httpx/test_httpx.py	72.44% <63.33%> (-1.41%)	:arrow_down:
ddtrace/contrib/trace_utils.py	95.12% <100.00%> (+0.35%)	:arrow_up:
ddtrace/ext/http.py	100.00% <100.00%> (ø)
...ests/contrib/aiohttp_jinja2/test_aiohttp_jinja2.py	85.29% <100.00%> (ø)
tests/contrib/django/test_django_appsec.py	100.00% <100.00%> (ø)
tests/contrib/django/test_django_snapshots.py	100.00% <100.00%> (ø)
tests/contrib/pylons/test_pylons.py	99.44% <100.00%> (+<0.01%)	:arrow_up:
tests/contrib/pyramid/test_pyramid.py	98.78% <100.00%> (ø)
... and 1 more

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[mergify[bot]]

@avara1986 this pull request is now in conflict 😩

[mergify[bot]]

@avara1986 this pull request is now in conflict 😩

[mergify[bot]]

@avara1986 this pull request is now in conflict 😩

[mergify[bot]]

@avara1986 this pull request is now in conflict 😩