multiple executor map entries

Hi,

please add an option to configure multiple commands for filetypes:

this would be usefull if you need to execute your code in different environments.

Examples:
- running bash script on local machine or remote server
- running sql scripts on different databases (sqlplus, mysql, psql )
- compiling for production or debug
- use different versions of a tool

If you have multiple tools configured, the code runner will ask you wich tool you want to use.

You should be able to configure the order, in which the tools will be listed.
(priority config, alphabetical or recently used)

Configuration example:
`
{
"code-runner.executorMap": {
"bash": {
"local" : "bash",
"remote" : "ssh"
},
"sql": {
"mysql" : "mysql",
"oracle" : "sqlplus",
"postgreSQL" : "psql"
},
}
}
`

Start by locating how the extension reads code-runner.executorMap and selects an executor for a file type. Review the current configuration and execution flow before defining how multiple named commands and their ordering should work. Done means users can configure multiple commands, choose among them, and control the displayed order.

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