Filters should not use fixed number of lines/specs/matches

The filters implemented in tr_filter.c/.h are currently implemented using a fixed number of entries for the number of filter lines, specs within each filter line, and matches for each spec. This was done for expediency, but should be refactored to allow arbitrary numbers of entries at each level.

The original implementation used 8 for each, but that was immediately too small for the number of matches in our test configuration (specifically, we needed more matches). I will increase that for now.