Separate test launch from test coverage

[a-yumashin]

Introduced two new options: --mode and --sessionName. Now it's possible to perform two separate launches of the executable, with the same session name provided - that's good if we want to run tests by some other means rather than by this executable via the --query option. For example:

SqlCoverCore.exe -m OnlyStart -s some_unique_id_1 -c Get-CoverTSql -e Export-OpenXml -k "Server=server_name_1;Trusted_Connection=True;" -d database_name_1
SqlCoverCore.exe -m OnlyStart -s some_unique_id_2 -c Get-CoverTSql -e Export-OpenXml -k "Server=server_name_2;Trusted_Connection=True;" -d database_name_2

(here you may run any tests from any tools at servers server_name_1 and server_name_2)

SqlCoverCore.exe -m OnlyStopAndReport -s some_unique_id_1 -c Get-CoverTSql -e Export-OpenXml -k "Server=server_name_1;Trusted_Connection=True;" -d database_name_1
SqlCoverCore.exe -m OnlyStopAndReport -s some_unique_id_2 -c Get-CoverTSql -e Export-OpenXml -k "Server=server_name_2;Trusted_Connection=True;" -d database_name_2

Changes proposed in this pull request:

• described above

How to test this code:

• described above (see after "For example:")

Has been tested on:

• SQL Server 2017

[lastlink]

@a-yumashin make sure to update the yml pipeline file for it to pass after this update

[a-yumashin]

@a-yumashin make sure to update the yml pipeline file for it to pass after this update

I'm afraid I got no experience with this stuff. Could you please explain in more details what should I do and where? )