various: Port to GtkBuilder templates

Currently we are using non-template builder ui files for UI for UI, we fetch all widgets and connect signal callbacks which is error prone. Also, we create custom structs to pass data to some other functions and we have to deal with properly freeing them when done, which makes to code logic harder to read and understand.

Porting to GtkBuiler templates shall make the code be a proper GObject class and has the following benifits:

• all Object class members are initialized to 0/NULL by default and so we don't have to initialize them
• we can bind signal callbacks and property changes with in the ui files.
• GtkBuilder itself handles binding variables to appropriate widgets, and thus we will find bugs early during run time. ie, before the widget is even used.
• The code logic is easier to understand
• We don't want to pass random pointers to pass data and it's easy to free the data at once.

This commit also removes support for buttons with stock icons and replaces gtk_dialog_run() so that it would be easier to port to GTK4

For unlock-dialog, I couldn't test tcrypt decryption.