fix(starlette): fixes incorrect handling of path/root_path in older starlette versions

[zarirhamza]

root_path now correctly contains the duplicated mounted path found in path for starlette > v0.34 as per ASGI standards

Previously, there was no duplication when mounting applications on starlette. This required us to set tags using both root_path and path. However, this was later fixed in later versions of starlette leading to duplication.

Logic is now implemented such that the ASGI middleware follows the specifications and only takes the path into consideration for tracing and older versions of starlette have their spans edited within the starlette integration

Changes are also made to the testing snapshots to account for the TestClient change after v0.20 in starlette

Checklist

• Change(s) are motivated and described in the PR description
• Testing strategy is described if automated tests are not included in the PR
• Risks are described (performance impact, potential for breakage, maintainability)
• Change is maintainable (easy to change, telemetry, documentation)
• Library release note guidelines are followed or label changelog/no-changelog is set
• Documentation is included (in-code, generated user docs, public corp docs)
• Backport labels are set (if applicable)
• If this PR changes the public interface, I've notified @DataDog/apm-tees.
• If change touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.

Reviewer Checklist

• Title is accurate
• All changes are related to the pull request's stated goal
• Description motivates each change
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Change is maintainable (easy to change, telemetry, documentation)
• Release note makes sense to a user of the library
• Author has 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

[mabdinur]

Can we link to the starlette issue here. This will make this problem easier to track

Suggested change

	# If we are on a version of starlette that is less than 0.34, we need to fix the span url
	# since starlette sets the incorrect values for path/root_path
	# If we are on a version of starlette that is less than 0.34, we need to fix the span url
	# since starlette sets the incorrect values for path/root_path

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: zarir/starlette-fix-and-upgrade
Commit report: d3eec4b
Test service: dd-trace-py

✅ 0 Failed, 171103 Passed, 1038 Skipped, 11h 35m 10.04s Total duration (15m 0.11s time saved)