<!--
Please provide as much information as possible about what your PR aims
to do.
PRs with no description will most likely be closed until more
information is provided.
If you're planing on changing fundamental behaviour or add big new
features, please open a GitHub Issue first before starting to work on
it.
If it's not something big and you still want to contact us about it,
feel free to do so !
-->
### Problem description
<!-- Describe the bug that you fixed/feature request that you
implemented, or link to an existing issue describing it -->
Implement a Linux backend for the ProcessMemoryProvider plugin.
### Implementation description
<!-- Explain what you did to correct the problem -->
Most of the provider code is the same between Windows and Linux. The
primary differences are:
- enumerate PIDs in `/proc/` to get the process list
- use `/proc/<PID>/cmdline` as the process name
- parse `/proc/<PID>/maps` to get the module list
- reading/writing from memory is done using
`process_vm_readv`/`process_vm_writev`
NOTE: `sudo setcap CAP_SYS_PTRACE=+eip build/imhex` must be run to give
the binary permission to read another process' memory. Running as root
user should also work but I would not recommend it.
### Additional things
The existing translations keys no longer match since I moved the plugin
from `windows` to `builtin`.
I'm not well versed in C++ so I attempted to keep my changes rather
simple. Feedback is very welcome.
---------
Co-authored-by: WerWolv <werwolv98@gmail.com>
### Problem description
Ref #1210
### Implementation description
Call
[`SetFileTime()`](https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-setfiletime)
everytime `FileProvider::save()` is called.
### Additional things
I moved the call to `File::close()` from `FileProvider::open()` to
`FileProvider::close()` because `SetFileTime()` requires a file handler
as input, so I need `File::m_file` to be valid.
