QL: Add support for unsigned_long field type

[astefan]

Following #60050 merge, we should consider adding support for it in both EQL and SQL.

[elasticmachine]

Pinging @elastic/es-ql (:Query Languages/EQL)

[elasticmachine]

Pinging @elastic/es-ql (:Query Languages/SQL)

[stu-elastic]

Unsigned long support has been added in #76519 which has been backported to v7.15

You can use doc['ul'].value which will return a java long (which means values greater than 2^63 are negative), or the fields api equivalent field('ul').getValue(default).

You can also treat it as a BigInteger, field('ul').as(Field.BigInteger).getValue(default). For examples, check out the yamlRestTest