starlette: use wrapt for patching instead of class replacement

[SrdjanLL]

Description

Moving starlette instrumentation to patch Starlette.__init__ method using wrapt instead of doing the class replacement to prevent potential ordering issues.

Left the behaviour of manual instrumentation methods of StarletteInstrumentor to work as it did before.

The core issue where this surfaced (#3476) has already been closed, but this was still a relevant improvement

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Unit tests

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 updated
• Documentation has been updated

[xrmx]

So if we don't have an ordering issue with other instrumentations then the value of switching to wrapt would be the removal of these top level imports and push them at a later time or move them under type checking. Do you see this achievable?

[codefromthecrypt]

Would love a fix to the issue, if it is this, so that we don't need to manually do StarletteInstrumentor.instrument_app(app). There are an increasing number of applications using starlette due to the prevalence of JSON-RPC in genai agents, such as Google A2A.

Right now, you have to manually instrument the app in order to use "zero code instrumentation" (and successfully join agents in the same trace). The combination of "zero code" and also needing to patch your code doesn't make any sense. cc @aabmass

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