[Bug]: COSI build with systemd-boot doesn't detect loader entries on EFI partition

**Bug Description**
COSI build doesn't extract UAPI type 1 (non-UKI) loader entries (/loader/entries/) from EFI partition.  MIC only checks the legacy boot partition for loader entries and will fail if none are present despite valid loader entries on EFI partition.  systemd-boot supports the EFI directory for loader entries files.  Same setup with VHDX as the output functions correctly

**Expected behavior**
COSI build succeeds

**Actual behavior**
```shell
FATA[0042] image customization failed:
failed to collect OS information:
failed to extract bootloader metadata:
systemd-boot detected, but no supported boot entries found
```

**Logs / Output**
See above

**Reproduction Steps**
Steps to reproduce the behavior:

1. Command line used (please paste the full command):
```shell
customize 
--build-dir
--config-file /path/to/mic.yaml 
--image-file base.vhdx 
--log-level debug 
--output-image-format cosi 
--output-image-file vm.cosi 
--rpm-source
```
2. Relevant portion of the configuration file (YAML/JSON). Please redact any
  secrets:
```yaml
os:
hostname: my-vm
bootloader:
   resetType: hard-reset
packages:
   install:
     - systemd-boot
...
```
3. Any additional steps:
Remove any preexisting grub packages and configs if present.  Install systemd-boot on EFI partition and also install the loader entries file on EFI partition. All required boot artifacts (kernel, initrd) are present on EFI partition as described by entries file.

**Environment**
- How was Image Customizer invoked? container image
- Host OS and version Azure Linux 3.0:
- Host architecture x86_64:
- Base image used: vhdx
- Target image format: COSI

**Image Customizer version**
1.6.0

**Additional context**
When I set the output to `vhdx` instead of COSI, a hyperv VM boots just fine with this setup.

[systemd-boot docs](https://www.man7.org/linux//man-pages/man7/sd-boot.7.html)
```text
      Boot entry description files following the UAPI.1 Boot Loader
      Specification[1] are read from /loader/entries/ on the ESP and the
      Extended Boot Loader partition.
```

Code in question is probably [this](https://github.com/microsoft/azure-linux-image-tools/blob/main/toolkit/tools/pkg/imagecustomizerlib/cosicommon.go#L460)

Start at toolkit/tools/pkg/imagecustomizerlib/cosicommon.go around the linked line and trace how COSI collects systemd-boot metadata and searches for loader entries. Reproduce the issue with the provided customize command and EFI-partition layout; done means the COSI build succeeds when UAPI type 1 entries exist on the EFI partition.

Written by the indexing model from the issue text.