fix(trajectory_follower_nodes): switch to isolated gtests

[maxime-clem]

Description

This PR attempts to fix #649 by running tests of package trajectory_follower_nodes in "isolated" mode.

Such solution has been investigated before: https://gitlab.com/autowarefoundation/autoware.auto/AutowareAuto/-/issues/1470

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[codecov]

Codecov Report

Merging #661 (1816f45) into main (dc682e6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #661   +/-   ##
=======================================
  Coverage   10.59%   10.59%           
=======================================
  Files         734      734           
  Lines       51719    51719           
  Branches     6596     6596           
=======================================
  Hits         5482     5482           
  Misses      41777    41777           
  Partials     4460     4460           

Flag	Coverage Δ		*Carryforward flag
differential	35.34% <ø> (?)
total	10.59% <ø> (ø)		Carriedforward from dc682e6

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