fix(instrumentation-http): skip malformed forwarded headers

[pmlanger]

Which problem is this PR solving?

Skips malformed forwarded headers instead of throwing an uncaught exception.

Fixes #5095

Short description of the changes

Introduce parseForwardedHeader in experimental/packages/opentelemetry-instrumentation-http/src/utils.ts which wraps forwarded-parse and returns an empty array on any caught exception.

Type of change

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?

First, wrote a test that broke the instrumentation in the expected way (throwing ParseError: Unexpected end of input).
Then, fixed it and confirmed the test passes.

Checklist:

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

[linux-foundation-easycla]

• ✅login: pmlanger / (61f4855)

The committers listed above are authorized under a signed CLA.

[omBratteng]

I think this would solve an issue we stumbled upon, where the forwarded header contains a base64 encoded value that ends with a =, and technically makes it malformed.

Could you add a test case for this value?

for=127.0.0.1;host=something.vercel.app;proto=https;sig=0QmVhcmVyIDc3MGNlY2M5YTIyZjJmNTg1ZGNlOTQ1NTUzMTIwMGFkMmZhOGEzZGNiM2M2NWQ4ZDk2ZGI5MDExMDkzMjkwYWM=;exp=1730556049