Script: ulong support via Fields API (boxing)

[stu-elastic]

get<T>(defaultValue) version of #76205

Exposes unsigned long via the fields API.

Users must choose how to consume unsigned longs, either as regular java longs, where
the upper half of the range is treated as negative, or as BigIntegers.

Fields API now requires explicit typing until we do some work in painless work to allow duck
typing.

script_fields is not yet implemented with the fields API.

// Typed field
field('ul').asBigIntegerField().getValue(BigInteger.valueOf(1000))
field('ul').asBigIntegerField().getBigInteger(BigInteger.valueOf(1000))

field('ul').asLongField().getValue(1000L)
field('ul').asLongField().getLong(1000L)


// Typed value
field('ul').getBigInteger(BigInteger.valueOf(1000))
field('ul').getLong(1000L)

// Def value
field('ul').getValue(BigInteger.valueOf(1000))
field('ul').getValue(1000L)

Fixes: #64361

[mark-vieira]

@elasticmachine retest this please

[stu-elastic]

closed in favor of #76519