lib/uri: Make parsing URIs more case insensitive
When parsing URIs we should generally be case insensitive where possible. The longer discussion can be found at the qemu-block archives linked below.
This commit makes fairly minimal changes so that we parse the scheme and query parameters like "socket=" case insensitively, and adds a simple test.
Note when generating or documenting URIs we still always use lowercase. This is intentional.
Reported-by: Eric Blake See: https://lists.nongnu.org/archive/html/qemu-block/2024-03/msg00635.html