examples/lua*: adapt to the blob mechanism

[aabadie]

Contribution description

This PR adapts the lua examples so that they now use the blob mechanism available in the build system instead of manually generating the header files containing the lua code.
The approach is already done with micropython and javascript examples.

Testing procedure

lua examples are still functional.

Examples on native:

`examples/lua_basic`

make -C examples/lua_basic/ all term
make: Entering directory '/work/riot/RIOT/examples/lua_basic'
Building application "lua_basic" for "native" with MCU "native".

make[1]: Nothing to be done for 'prepare'.
make[1]: Nothing to be done for 'prepare'.
"make" -C /work/riot/RIOT/pkg/lua
"make" -C /work/riot/RIOT/examples/lua_basic/bin/pkg/native/lua -f /work/riot/RIOT/pkg/lua/Makefile.lua
"make" -C /work/riot/RIOT/pkg/tlsf
"make" -C /work/riot/RIOT/examples/lua_basic/bin/pkg/native/tlsf -f /work/riot/RIOT/Makefile.base
"make" -C /work/riot/RIOT/boards/native
"make" -C /work/riot/RIOT/boards/native/drivers
"make" -C /work/riot/RIOT/core
"make" -C /work/riot/RIOT/cpu/native
"make" -C /work/riot/RIOT/cpu/native/periph
"make" -C /work/riot/RIOT/cpu/native/stdio_native
"make" -C /work/riot/RIOT/cpu/native/vfs
"make" -C /work/riot/RIOT/drivers
"make" -C /work/riot/RIOT/drivers/periph_common
"make" -C /work/riot/RIOT/pkg/lua/contrib
"make" -C /work/riot/RIOT/sys
"make" -C /work/riot/RIOT/sys/auto_init
   text	   data	    bss	    dec	    hex	filename
 290708	   2724	  58736	 352168	  55fa8	/work/riot/RIOT/examples/lua_basic/bin/native/lua_basic.elf
/work/riot/RIOT/examples/lua_basic/bin/native/lua_basic.elf  
RIOT native interrupts/signals initialized.
LED_RED_OFF
LED_GREEN_ON
RIOT native board initialized.
RIOT native hardware initialization complete.

main(): This is RIOT! (Version: 2020.07-devel-1406-gd191b)
Lua RIOT build
Hello world, this is lua!
Lua interpreter exited
^C
native: exiting

`examples/lua_REPL`

make -C examples/lua_REPL/ all term
make: Entering directory '/work/riot/RIOT/examples/lua_REPL'
Building application "lua_repl" for "native" with MCU "native".

[INFO] cloning lua
git-cache: cloning from cache. tag=commite354c6355e7f48e087678ec49e340ca0696725b1-443128
[INFO] updating lua /work/riot/RIOT/examples/lua_REPL/bin/pkg/native/lua/.pkg-state.git-downloaded
echo e354c6355e7f48e087678ec49e340ca0696725b1 > /work/riot/RIOT/examples/lua_REPL/bin/pkg/native/lua/.pkg-state.git-downloaded
[INFO] patch lua
[INFO] cloning tlsf
git-cache: cloning from cache. tag=commita1f743ffac0305408b39e791e0ffb45f6d9bc777-443185
[INFO] updating tlsf /work/riot/RIOT/examples/lua_REPL/bin/pkg/native/tlsf/.pkg-state.git-downloaded
echo a1f743ffac0305408b39e791e0ffb45f6d9bc777 > /work/riot/RIOT/examples/lua_REPL/bin/pkg/native/tlsf/.pkg-state.git-downloaded
[INFO] patch tlsf
"make" -C /work/riot/RIOT/pkg/lua
"make" -C /work/riot/RIOT/examples/lua_REPL/bin/pkg/native/lua -f /work/riot/RIOT/pkg/lua/Makefile.lua
"make" -C /work/riot/RIOT/pkg/tlsf
"make" -C /work/riot/RIOT/examples/lua_REPL/bin/pkg/native/tlsf -f /work/riot/RIOT/Makefile.base
"make" -C /work/riot/RIOT/boards/native
"make" -C /work/riot/RIOT/boards/native/drivers
"make" -C /work/riot/RIOT/core
"make" -C /work/riot/RIOT/cpu/native
"make" -C /work/riot/RIOT/cpu/native/periph
"make" -C /work/riot/RIOT/cpu/native/stdio_native
"make" -C /work/riot/RIOT/cpu/native/vfs
"make" -C /work/riot/RIOT/drivers
"make" -C /work/riot/RIOT/drivers/periph_common
"make" -C /work/riot/RIOT/pkg/lua/contrib
"make" -C /work/riot/RIOT/sys
"make" -C /work/riot/RIOT/sys/auto_init
   text	   data	    bss	    dec	    hex	filename
 294541	   2780	  90640	 387961	  5eb79	/work/riot/RIOT/examples/lua_REPL/bin/native/lua_repl.elf
/work/riot/RIOT/examples/lua_REPL/bin/native/lua_repl.elf  
RIOT native interrupts/signals initialized.
LED_RED_OFF
LED_GREEN_ON
RIOT native board initialized.
RIOT native hardware initialization complete.

main(): This is RIOT! (Version: 2020.07-devel-1406-gd191b)
Using memory range for Lua heap: 0x565b5090 - 0x565becd0, 4 bytes
This is Lua: starting interactive session

Welcome to the interactive interpreter
L> help
L> h
L> 1 + 2
3
L> ^C
native: exiting

Issues/PRs references

closes #11497 (blobs mechanism already available and lua examples are adapted)

[fjmolinas]

ACK, tested both examples on native:

LED_RED_OFF
LED_GREEN_ON
RIOT native board initialized.
RIOT native hardware initialization complete.

main(): This is RIOT! (Version: 2020.07-devel-1407-gead8b8-pr-14332)
Using memory range for Lua heap: 0x5663f090 - 0x56648cd0, 4 bytes
This is Lua: starting interactive session

Welcome to the interactive interpreter
L> help
L> a
L> 1
1
L> help
L> 1 + 2
3
L> 

LED_RED_OFF
LED_GREEN_ON
RIOT native board initialized.
RIOT native hardware initialization complete.

main(): This is RIOT! (Version: 2020.07-devel-1407-gead8b8-pr-14332)
Lua RIOT build
Hello world, this is lua!
Lua interpreter exited
hlep