SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This fixes an issue were "Find in Files" would not use the up-to-date
content of a file with unsaved changes.
The issue existed because 'FindInFilesWidget' uses
Project::for_each_text_file, which retrieves files by their absolute
path. However, when a file is opened in an Editor, it is created with
a relative path.
This caused us to store two ProjectFile objects that refer to the same
file - one with a relative path and one with an absolute path.