[data.query.filters] Create expression function for filters & add toAst method

[lukeelmers]

Part of #61769
Blocks #65988

• create field expression function that takes name, type and script and returns kibana_field type
• create phraseFilter expression function that takes value (multi field, to support phrases filter as well) and field (of kibana_field type) parameters and returns kibana_filter
• create range function that takes lt, gt, lte, gte paramteres and returns kibana_range
• create rangeFilter expression function, that takes field and range (kibana_range type) and returns kibana_filter
• create existsFilter expression function, that takes field and returns kibana_filter
• create filtersToExpressionAst utility function which takes kibana filters array and returns array expression functions for it
• use all above in kibana_context function and update embeddable to_ast

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)