Add support for multiple custom gatewares to be included in debian custom-gateware package

This merge requests includes two enhancements when using forked gateware repositories:

• Allow the name of the custom gateware to be changed from my_custom_fpga_design to a name of the user's choice.
• Allow multiple custom gateware programming files to be generated and distributed from the same forked repo.

These changes make the gateware forked repositories more appealing for distributing custom project gateware since the gateware name no longer has to be my_custom_fpga_design but can be given a more representative name for the gateware project.

These changes dynamically generate a debian-custom/bbb.io-gateware-my-custom-fpga-design.install file as part of the build-job artifacts, listing the programming files for all gateware options specified by yaml files in gateware/custom-fpga-design. This generated debian-custom file is used as part of the Page/Deploy

As an example if custom-fpga-design includes 4 gateware yaml configuration file as follows:

• custom_fpga_design_b.yaml
• custom_fpga_design_c.yaml
• custom_fpga_design_d.yaml
• my_custom_fpga_design.yaml

Then installing the custom gateware via apt install will result in the following gateware programming files being installed in /usr/share/beagle/gateware:

└── gateware
     ├── board-tests
     ├── custom_fpga_design_b
     ├── custom_fpga_design_c
     ├── custom_fpga_design_d
     ├── default
     ├── minimal
     ├── my_custom_fpga_design
     └── robotics