Backport 5.1: New pipeline functions remove_single_field and remove_multiple_fields

[patrickmann]

5.2 backport of #19268

• new pipeline functions remove_single_field and remove_multiple_fields

• CL

• improve rulebuilder descriptions

• compile regex and other feedback changes

• pre-compile pattern

• UI string improvements

(cherry picked from commit https://github.com/Graylog2/graylog2-server/commit/4a1cbb4dcb8563a6686e0709040dea75ed831359)