fix(param): use C-style array for parameters_volatile/readonly

NuttX builds do not provide the C++17 <array> header, so the generated
px4_parameters.hpp failed to compile on every NuttX board (px4_fmu-v5,
nxp_fmuk66-v3, modalai voxl2 SLPI, etc.) with:

    fatal error: array: No such file or directory

Drop std::array in favour of plain C arrays, which range-based for
already supports and which the embedded toolchains can compile. The
length is no longer needed in the type because the generator now
pre-filters volatile_params and readonly_param_names, and an empty
array would have been ill-formed under either spelling.

Signed-off-by: Nuno Marques <n.marques21@hotmail.com>

src/lib/parameters/templates/px4_parameters.hpp.jinja

@@ -2,7 +2,6 @@
 
 #include <math.h> // NAN
 
-#include <array>
 #include <stdint.h>
 #include <parameters/param.h>
 
@@ -39,13 +38,13 @@ static constexpr param_type_t parameters_type[] = {
 {%- endfor -%}
 };
 
-static constexpr std::array<params, {{ volatile_params | length }}> parameters_volatile {
+static constexpr params parameters_volatile[] = {
 {% for param in volatile_params %}
 	params::{{ param.attrib["name"] }},
 {% endfor %}
 };
 
-static constexpr std::array<params, {{ readonly_param_names | length }}> parameters_readonly {
+static constexpr params parameters_readonly[] = {
 {% for param_name in readonly_param_names %}
 	params::{{ param_name }},
 {% endfor %}