.gitlab/ci/build-inside-vm.sh:
Expand the script to allow building based on mkarchiso's buildmodes.
Accept two parameters now: profile and buildmode.

Add gitlab collapsable sections by adding specific printfs for it to all functions.
Add extglob to be able to more specifically target files.
Change `create_checksums()` to also generate the legacy md5 and sha1 checksums.
Change `create_checksums()` and `create_zsync_delta()` to accept and process an unspecified amount of files as
parameters.
Change `create_zsync_delta()` to lower the blocksize when creating a file for the bootstrap image.
Change `create_metrics()` to create metrics depending on build mode.
Rename `create_temp_pgp_key()` to `create_ephemeral_pgp_key()`.
Add `create_ephemeral_codesigning_key()` to create a codesigning key, that is used to sign the netboot artifacts.
Change `run_mkarchiso()` to also create an ephemeral codesigning key before running mkarchiso and to run
`create_checksums()` and `create_zsync_delta()` with files depending on build mode.

.gitlab/ci/build-host.sh:
Call `build-inside-vm.sh` using the PROFILE and BUILDMODE environment variables as parameters.