Add feature to extract and merge a mysql-shell tarball into a regular one

[datacharmer]

MySQL distributes MySQL shell as a separate tarball. Yet, the shell is needed to run operations on MySQL document stores and InnoDb clusters. As of today, the MySQL team does not want to merge the two products.

It is possible to unpack the MySQL shell and add the pieces to an unpacked binary tarball, but it's a time consuming and error prone operation.

There should be a new option under unpack:

dbdeployer unpack --shell mysql-shell-8.0.12-macos10.13-x86-64bit.tar.gz 

This command will unpack the shell tarball in a temporary directory, then merge the files under the directory $SANDBOX_BINARY/8.0.12 (which contains the database binaries and must already exist.)

If we want to put the shell under a different database tree, we can use the additional option:

dbdeployer unpack --shell \
    --target-server=labs8.0.21 \
    mysql-shell-8.0.12-macos10.13-x86-64bit.tar.gz 

Also in this case, the directory $SANDBOX_BINARY/labs8.0.21 must exist and contain valid server binary files.

[datacharmer]

implemented in version 1.9.0