Previously, the API required to create HttpTrace instances was
package-private. This made it difficult to implement an
HttpTraceRepository that persists the HttpTrace instances
rather than holding them in memory as it inhibited recreation of the
instances when they read from the persistent store.
This commit adds public constructors to HttpTrace and related classes
to enable recreation of an HttpTrace. The package-private methods for
mutating properties have not been made public to ensure that the
public API remains immutable.
Closes gh-14726
1d2f069580