http: preserve cookie jar for TLS clients

[Rememorio]

Summary

• Preserve the configured http.Client CookieJar when constructing TLS-specific HTTP clients.
• Add regression coverage for CookieJar handling on TLS requests.

Tests

• go test ./http -run TestTLSClientInheritsCookieJar -count=1
• go test ./http -count=1
• go test ./... -count=1

Close #202

[WineChord]

LGTM