This patch has three logical parts:

1. Remove the 'mysql_install_db' executable and all references to it from
   elsewhere. Remove associated MTR tests, unit tests, comments mentioning
   it, as well as additional source code used only by that executable.

   Rewrite 'scripts/mysqld_multi.sh' to use 'mysqld --initialize' rather
   than 'mysql_install_db'.

   Note: Usage of 'mysql_install_db' from MySQL Cluster test environment
         will be fixed by  Cluster devs outside the scope of this WL.

2. Remove the deprecated '--bootstrap' option, and the '--install-server'
   option (which has not been released). Replace the variables
   representing these options by the variable representing the
   '--initialize' option.

   Update or remove tests and scripts referring to these variables.

3. Remove support for MTR_VERSION=1. This is dependent on the
   deprecated '--bootstrap' option, and is therefore removed.