This change alters the way we resolve the data-dir and initialized dolt processes. It originated from discovering that the tmp dir replace test at startup was leaving a test file in the current working directory. Long story short - the resolution of data-dir was too late in the process startup when sql-server was starting.

External behavior which will change:

1. Specifying data_dir in sql-server config file will correctly test the ability to rename files on the same partition, and override the TMPDIR environment variable when necessary, using $DATADIR/tmp when the user specified directory is on the wrong partition
2. Fail to start the server when the data-dir is specified multiple times. This will result in server startup failure for existing deployments which "work" (we choose the data-dir deterministically now, but not in the expected precedence)

Fixes: #8498