avoiding multiple string creation #1

changed:
src/modules/utils/panel/screens/PrepareScreen.cpp
src/modules/utils/panel/screens/PrepareScreen.h

std::string is 8 Bytes + heap allocations if set <-> const char * is 4 bytes + reuse of c string literal
command is only assigned in line 67 to 73 in PrepareScreen.cpp there are const char [] string literals assigend only.

They do not need to be put into a string, if the string's c_str() (const char*) is passed to send_command.
the assigned literal is sufficient, too.

saves 4 bytes of RAM (heap) (all the time) + strlen+1+padding bytes RAM (heap) (temporarily)
also saves time for allocation and deallocation when a command is executed
avoiding multiple string creation #2

changed:
src/modules/utils/panel/screens/CustomScreen.cpp
src/modules/utils/panel/screens/CustomScreen.h

std::string is 8 Bytes + heap allocations if set <-> const char * is 4 bytes + reused c string
in line 83 in CustomScreen.cpp there is always a const char * string pointer assigend
They do not need to be put into a string if the string's c_str() (const char*) is passed to send_command.
the assigned ptr is sufficient, too.

saves 4 bytes RAM (heap) (all the time) + strlen+1+padding bytes RAM (heap) (temporarily)
also saves time for allocation and deallocation
move ModifyScreen's MenuItem's inc,min,max to .text

changed:
src/modules/utils/panel/Panel.cpp
src/modules/utils/panel/screens/MainMenuScreen.cpp
src/modules/utils/panel/screens/ModifyValuesScreen.cpp
src/modules/utils/panel/screens/ModifyValuesScreen.h

replace float, float, float by a pointer to an array of float in ModyfyValueScreen::MenuItemType
the arrays are only stored in .text and will not be copied to heap when the menu item is created
this saves 8 bytes of RAM (heap) per menu entry (currently 9 items) = 72 bytes
the arrays can be reused for several menu items (temp, steps/mm) which saves .text