fix: show error message if duplicate sfn name

[woorui]

Description

Data stream links their connections, ff two identical named sfn are connected to the same zipper, then the preceding sfn should be closed.

[vercel]

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1 Ignored Deployment

Name	Status	Preview	Comments	Updated (UTC)
yomo	⬜️ Ignored (Inspect)	Visit Preview		Sep 6, 2023 8:42am

[codecov]

Codecov Report

Merging #582 (bf8acd5) into master (8d4eddf) will decrease coverage by 0.26%.
The diff coverage is 59.23%.

@@            Coverage Diff             @@
##           master     #582      +/-   ##
==========================================
- Coverage   63.31%   63.06%   -0.26%     
==========================================
  Files          39       40       +1     
  Lines        2988     3097     +109     
==========================================
+ Hits         1892     1953      +61     
- Misses        963     1004      +41     
- Partials      133      140       +7     

Files Changed	Coverage Δ
core/client.go	70.68% <0.00%> (-1.68%)	⬇️
pkg/frame-codec/y3codec/rejected_frame.go	72.72% <ø> (+0.85%)	⬆️
core/control_stream.go	59.77% <52.38%> (-0.78%)	⬇️
core/data_stream.go	64.13% <57.14%> (-35.87%)	⬇️
pkg/frame-codec/y3codec/goaway_frame.go	72.72% <72.72%> (ø)
core/stream_group.go	75.55% <100.00%> (+0.27%)	⬆️
pkg/frame-codec/y3codec/codec.go	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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