Move librz/cons/grep.c (~) command from the RzCons to the RzCore

[XVilka]

It has nothing to do with the RzCons and belongs along with other commands handling, in RzCore. It also should be better integrated with the rzshell.

• librz/cons/grep.c
• librz/include/rz_cons.h
• librz/core/cmd.c

See also：

• librz/cons/* (TUI library/) - remove global state #276
• Remove the use of sdb_json_* API #985
• Tracking porting the commands parser to the tree-sitter-based one #1342