fix: graphql post request route matching exception

[AlinsRan]

Description

Reuse of match_opts causes the value of the next request to overwrite the value of the current request. GraphQL requests call the ngx.req.read_body API, which is a non-blocking call. If the request body has not been fully read (for example, if the body size exceeds the nginx buffer), the coroutine will yield. If there are other requests during this time period, match_opts will be contaminated by other requests, resulting in matching the wrong route.

Fixes: #10197

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)