fix: data race in AnalyzeTypeAddr for v0.10.4

[sunadoi]

fix #529

Issue Description

• runtime.AnalyzeTypeAddr() writes to a global variable alreadyAnalyzed
• runtime.AnalyzeTypeAddr() could be called once each from both initDecoder and initEncoder
• When initDecoder and initEncoder were called simultaneously from different goroutines, it was detected as a data race, causing flaky test failures

Solution

Modified runtime.AnalyzeTypeAddr to use sync.Once instead of a global variable to ensure thread-safe initialization

Verification

Ran tests in my project using the following command:

go test -v -race ./... -count=1

Tests that were flaky in v0.10.4 now pass consistently with the fixed code
(verified with over 50 consecutive successful runs)

[sunadoi]

@goccy
Would you review this PR when you have a moment?