Tracking: Process time temporal join

[chenzl25]

Implement process time temporal join based on the RFC: risingwavelabs/rfcs#49:

• FOR SYSTEM_TIME AS OF NOW() syntax. (feat(streaming): support temporal join part 3 #8480)
• Convert a logical join to a temporal join (Use a rule or directly implement in to_stream_plan? Need investigation). (feat(streaming): Temporal join part2 #8466)
• Stream Process time temporal join operator. (feat(streaming): Temporal join part2 #8466)
• Process time temporal join executor. (feat(temporal-join): Temporal join executor #8412)
• Loose temporal join restrictions to allow join condition containing only the prefix of the right table's pk. feat(stream): temporal join support pk prefix join condition #10627
• Covering Index selection for temporal join. feat(optimizer, stream): support index selection for temporal join #11019
• Secondary Index for temporal join

[chenzl25]

@wsx-ucb As we have already supported the process time temporal join, let's perform a benchmark analysis comparing the efficiency of stream hash join and process time temporal join. BTW, we can give a demo for process time temporal join, such as joining a Kafka stream with a materialized view backed by MySQL CDC. I think it is a good use case for our website doc.