common: json_to_s64 accept only valid JSON numbers

[guibsa]

bool str_to_s64 parses a decimal s64 from exactly buflen bytes; false on bad chars, overflow, leading +, hex like '0x...' . Similar behavior of json_to_u64 and str_to_u64. Tests added. Partially fixes #9377

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[Andezion]

run-utils-str_to_s64.c has no direct test like assert(!str_to_s64("+123", 3, &val)) or assert(!str_to_s64("0x1A", 4, &val)). it only tests --123 and +-123 (mixed/double signs), which is a different case, maybe worth adding something like +123 and a hex string

[Andezion]

Nice!

[Andezion]

common/test/run-utils-str_to_s64.c has #include <assert.h> and then #include <assert.h> and #include <stdint.h> again right after /* AUTOGENERATED MOCKS END */. <stdint.h> also looks unused? The test uses s64 and LL/ULL literals, not int64_t/INT64_MIN directly