test: expect scrubbed custom header values in e2e

[TerryHowe]

What this PR does

Fixes the 9 failing 1.1 registry users: when custom header is provided e2e specs that have broken main since the GHSA-5jhf-2qmf-m8c5 fix landed.

Why

That fix scrubs configured custom header names from --debug trace output, since --header is commonly used to pass credential headers:

• cmd/oras/internal/option/remote.go collects every --header name into sensitiveHeaders and passes them to trace.NewTransport
• internal/trace/transport.go replaces those values with *****

The e2e specs were not updated, so they still assert the raw values:

FoobarHeader = "\"Foo\": \"bar\"\n"
AbHeader     = "\"A\": \" b\"\n"

while the debug output now contains:

"A": "*****"
"Foo": "*****"

Every spec fails at test/e2e/internal/utils/match/request.go:58 with failed to match all headers. This affects attach, blob, manifest, pull, push, repo, tag, and both cp specs, and it fails on every PR branched after the fix (for example #2130, where it is unrelated to that PR's dependency bump).

The change

Expect the scrubbed values. The specs still verify that each custom header name is present on every matching request, which is what they were really guarding.

Verification

The full e2e suite could not be run locally (macOS AirPlay Receiver holds port 5000, so the test registry is unreachable), so the expected literals were checked directly against the real trace.logHeader with a throwaway unit test: "Foo": "*****"\n and "A": "*****"\n are both produced, and neither raw value leaks. CI on this PR exercises the real suite.

Note, not addressed here

The login spec in the same block passes only vacuously — it omits -d, so getRequests finds no requests and the matcher's loop never runs. Worth a follow-up.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.63%. Comparing base (799bb3e) to head (93796af).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2133      +/-   ##
==========================================
+ Coverage   87.44%   87.63%   +0.18%     
==========================================
  Files         139      139              
  Lines        5544     5651     +107     
==========================================
+ Hits         4848     4952     +104     
  Misses        417      417              
- Partials      279      282       +3     

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[sabre1041]

LGTM