[TSVB] Fix percentile rank math

[flash1293]

Fixes #131901

The code mapping series to variables for the math operation is assuming a percentile variable if percentileValueMatch matches the field name:

kibana/src/plugins/vis_types/timeseries/server/lib/vis_data/response_processors/series/math.js

Line 45 in 2a0366a

const percentileMatch = v.field.match(percentileValueMatch);

But it can actually be either percentile or percentile rank.

This PR adds a condition for these two cases and makes sure the downstream code receives the structure it expects.

[kibana-ci]

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[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[stratoula]

LGTM! I did an investigation yesterday and I made the same conslusion! Now it works fine 💯