VStream: Allow for automatic resume after reshard

[mattlord]

Description

When the scenario is detected, and we have the needed info, we will start a new copy resume phase to automatically resume when a Reshard has occurred since the last client stream.

Manual test on this branch:

./101_initial_cluster.sh; mysql < ../common/insert_commerce_data.sql; ./201_customer_tablets.sh ; ./202_move_tables.sh; ./203_switch_reads.sh; ./204_switch_writes.sh; ./205_clean_commerce.sh; ./301_customer_sharded.sh; ./302_new_shards.sh; ./303_reshard.sh; ./304_switch_reads.sh; ./305_switch_writes.sh

sleep 10

mysql -e "insert into customer (email) values ('mlord@planetscale.com')"
mysql -e "insert into customer (email) values ('mlord@planetscale.com')"

go run vstream_client.go

# In another shell
mysql -e "insert into customer (email) values ('mlord@planetscale.com')"

You'll see that we did not miss any post Reshard writes.

Related Issue(s)

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