fix(log-sanitize): return raw tables to avoid double delay_encode

[shreemaan-abhishek]

Description

apisix/utils/log-sanitize.lua's redact_params / redact_extra_opts already return a recycled delay_encode pool slot (a {data=, force=} table with a __tostring metamethod). The AI plugin call sites then wrap that slot in core.json.delay_encode(..., true) a second time:

• apisix/plugins/ai-proxy/base.lua:265
• apisix/plugins/ai-providers/base.lua:132
• apisix/plugins/ai-providers/base.lua:779

When the log line flushes, cjson encodes the inner wrapper table (cjson ignores __tostring), so the log emits the wrapper structure instead of the redacted JSON. Worse, delay_encode recycles a 16-slot pool, so by flush time the inner slot may already hold an unrelated request's data, risking stale or unredacted content from a different request in the logs. This triggers on every AI-proxy / ai-providers request log at info level.

This makes the sanitizer return raw tables and lets the single delay_encode already present at each call site do the encoding.

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 (no public behavior/docs change)
• I have verified that this change is backward compatible (the log content is now correct; no API change)