Docs update

I propose the following modifications to fix deprecated elements of the current documentation files:

• Substituted references from the Ibex to CVE2 when necessary.
• Updated OpenHW Group to OpenHW Foundation.
• Conversion to DrawIO SVG files, instead of pure SVG files, of the main blockdiagram, if_stage and de_ex_stage, to ease the edition of these diagrams.
• Update the documentation of integration file for the cve2_top, adding the eXtension InterFace and removing deprecated parameters.
• Updated the history.rst file, adding the fork from Ibex.
• Removed references to SecureIbex signals *_intg_i , that are not present on the RTL files.
• Removed references from other versions of the Register File, as we use only rtl/cve2_register_file_ff.sv at the moment.
• Removed reference to the Example System, as it was removed from the project.
• Fixed some typos