Provide an option to use `/bin/bash -l` in job scripts

Is your feature request related to a problem? Please describe.

In some clusters you may have to load the shell init script to run some commands (e.g. if module is a shell function, rather than an executable in PATH), or have some applications in PATH, etc.

As far as I understand, at the moment Parsl hardcodes

#!/bin/bash

as shebang line for most providers with no way to add the -l option, e.g.

parsl/parsl/providers/grid_engine/template.py

Line 1 in 2b1594c

template_string = """#!/bin/bash

Describe the solution you'd like

Provide an option to enable login shell. As a prior art in this area, ReFrame uses an environment variable called RFM_USE_LOGIN_SHELL and a configuration parameter called use_login_shell for this purpose.

Describe alternatives you've considered

N/A

Additional context

N/A

Is there any interest in this feature? I may be able to implement it myself with some directions (e.g., where such an option should be set?), but I won't waste my time if it isn't going to be accepted.