Add Support for Detecting Synthetic Source

[JacksonWeber]

Description

This pull request introduces experimental support for detecting synthetic traffic (such as bots and test monitors) in the OpenTelemetry Requests instrumentation by analyzing the User-Agent header. It adds logic to classify requests as originating from bots or test systems, sets a corresponding span attribute, and includes comprehensive tests to validate this behavior.

The most important changes are:

Synthetic User Agent Detection and Span Attributes:

• Added a function _detect_synthetic_user_agent in __init__.py to analyze the User-Agent header and classify requests as either "bot" or "test" traffic, prioritizing test patterns over bot patterns.
• Set the user_agent.synthetic.type span attribute when a synthetic user agent is detected, using new constants for attribute name and possible values. [1] [2]

Semantic Conventions:

• Introduced a new module semconv.py defining experimental semantic convention constants for synthetic user agent detection, including ATTR_USER_AGENT_SYNTHETIC_TYPE, USER_AGENT_SYNTHETIC_TYPE_VALUE_BOT, and USER_AGENT_SYNTHETIC_TYPE_VALUE_TEST.
• Updated imports in __init__.py to use these new constants from semconv.py.

Testing:

• Added a comprehensive test suite in test_user_agent_synthetic.py to verify detection logic for various user agent scenarios, including bots, test agents, normal browsers, case insensitivity, substring matches, and pattern priority.

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Tested via unit tests included in test_user_agent_synthetic.py

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated