Add JsonGenerator#writeNumber(char[], int, int) method

[vy]

As discussed in the relevant jackson-user thread, JsonGenerator#writeNumber() method lacks support for char[]. Introducing a JsonGenerator#writeNumber(char[] buffer, int offset, int length) will enable users to write numbers in their preferred format without incurring an extra allocation cost, e.g., as in JsonGenerator#writeNumber(String).

Note that #577 and #514 are relevant issues addressing a similar concern in broader sense.