Overhaul global filtering of participants

--participant-filter and --exclude-participant filter have had a couple
of bugs over the past few versions:

1. Both terms would apply to every single component, even components
   without the subject entity. These components would have all of their
   entries filtered out
2. Using --exclude-participant-filter would turn on regex matching
   mode for every single filter. This changed the meaning of the filters
   (e.g. allowing partial matches), leading to workflow disruption

The overhaul fixes both bugs, while improving the organization of the
input generation code.

Additionally, the documentation states the magic filter `regex_search:
True` can be used to enable regex searching for a block of filters. This
hasn't worked for the past few versions. Rather than fix it, the
behaviour has been silently disabled in preparation for an overhaul of
the regex filtering api

Resolves #303
Resolves #216

snakebids/core/datasets.py

@@ -446,6 +446,8 @@ def filter(
         if not isinstance(regex_search, bool):
             msg = "regex_search must be a boolean"
             raise TypeError(msg)
+        if not filters:
+            return self
         return attr.evolve(
             self,
             zip_lists=filter_list(self.zip_lists, filters, regex_search=regex_search),

snakebids/core/filtering.py

@@ -25,7 +25,7 @@ def filter_list(
 def filter_list(
     zip_list: ZipListLike,
     filters: Mapping[str, Iterable[str] | str],
-    return_indices_only: Literal[True] = ...,
+    return_indices_only: Literal[True],
     regex_search: bool = ...,
 ) -> list[int]:
     ...