pgsql: Recalculate search_path after ALTER ROLE.

Recalculate search_path after ALTER ROLE.

Renaming a role can affect the meaning of the special string $user, so
must cause search_path to be recalculated.

Discussion: https://postgr.es/m/[email protected]
Reviewed-by: Nathan Bossart, Michael Paquier
Backpatch-through: 11

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/9f3343e40df6fc92a3913eeb8e240e0f5c6a5cfc

Modified Files
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src/backend/catalog/namespace.c | 6 +-
src/test/isolation/expected/search-path-inval.out | 97 +++++++++++++++++++++++
src/test/isolation/isolation_schedule | 1 +
src/test/isolation/specs/search-path-inval.spec | 59 ++++++++++++++
4 files changed, 162 insertions(+), 1 deletion(-)