pgsql: Make new triggers tests more robust

Make new triggers tests more robust

Add explicit collation on the trigger name to avoid locale dependencies.
Also restrict the tables selected, to avoid interference from
concurrently running tests.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7c44b75a2a0705bf17d0e7ef02b1a0a769306fa5

Modified Files
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src/test/regress/expected/triggers.out | 49 +++++++++++++++++-----------------
src/test/regress/sql/triggers.sql      | 12 ++++++---
2 files changed, 33 insertions(+), 28 deletions(-)