pgsql: Set the stack_base_ptr in main(), not in random other places.

Set the stack_base_ptr in main(), not in random other places.

Previously we did this in PostmasterMain() and InitPostmasterChild(),
which meant that stack depth checking was disabled in non-postmaster
server processes, for instance in single-user mode. That seems like
a fairly bad idea, since there's no a-priori restriction on the
complexity of queries we will run in single-user mode. Moreover, this
led to not having quite the same stack depth limit in all processes,
which likely has no real-world effect but it offends my inner neatnik.
Setting the depth in main() guarantees that check_stack_depth() is
armed and has a consistent interpretation of stack depth in all forms
of server processes.

While at it, move the code associated with checking the stack depth
out of tcop/postgres.c (which was never a great home for it) into
a new file src/backend/utils/misc/stack_depth.c.

Discussion: https://postgr.es/m/2081982.1734393311@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c91963da1302e8dd490bde115f3956f7d2f1258d

Modified Files
--------------
src/backend/main/main.c | 6 ++
src/backend/postmaster/postmaster.c | 5 -
src/backend/tcop/postgres.c | 173 ------------------------------
src/backend/utils/init/miscinit.c | 7 --
src/backend/utils/misc/Makefile | 1 +
src/backend/utils/misc/meson.build | 1 +
src/backend/utils/misc/stack_depth.c | 197 +++++++++++++++++++++++++++++++++++
src/include/miscadmin.h | 8 +-
src/include/tcop/tcopprot.h | 5 -
9 files changed, 212 insertions(+), 191 deletions(-)