Fix process memory provider on Linux

[descawed]

Problem description

The process memory provider currently doesn't function correctly on Linux due to incorrect handling of the special procfs file /proc/<pid>/maps. I don't know if some of this behavior could vary by distro and/or kernel version, but I've observed the following issues in my Ubuntu 24.04 environment.

• The current code in master calls file.readString() which attempts to determine the size of the file by seeking to the end. However, procfs files don't have a defined size, so this fails with a return of -1. libwolv interprets this as the file size and attempts to allocate an enormous buffer, which results in an exception, so ultimately the process memory provider is unusable on the current code.
• The previous version of the code that went out in 1.35.4 was calling readString with a fixed maximum size of 0xF'FFFF. This avoids the seek issue, but when working with special files, a single read call isn't guaranteed to read the requested number of bytes even if that many bytes are available. In practice, on my machine, this call only ever reads the first few dozen lines of the file. So the feature works in this version, but it's unable to see the vast majority of the process' address space.
• On a more minor note, on rows in the maps file that have a filename, the filenames are visually aligned by padding spaces between the inode column and filename column. ImHex includes these spaces as part of the filename, resulting in most of the path being pushed out of the visible area of the window.

Implementation description

• To ensure the entire maps file is read, I've changed the code to read from the file in a loop until we stop getting data. I've also set a fixed limit on the maximum number of bytes to read in one go to avoid issues with trying to determine the file size.
• I've added a trim call to remove any padding around the filename.

Screenshots

Exception in file.readString() in current code (for some reason this also causes the window to become transparent):

Abridged memory region list in 1.35.4:

Complete memory region list after this PR:

Additional things

I was focused on fixing this ImHex feature here, but I wonder if some of this should be addressed in libwolv. Maybe readBuffer in file_unix.cpp should read in a loop until it has the requested number of bytes or encounters EOF/error?

[jumanji144]

Looks good, tests failing on fedora seems to be unrelated to the pr.

Will look into why the CI is failing, then merge