Fix PG CI: relocate calc_redo_mb to genci, escape start cmd

Two bugs surfaced during WSL Ubuntu 24 E2E validation of the PG CI port:

1. calc_redo_mb was defined only in src/mariadb/mariaci.tcl, so loading
   src/postgresql/pgci.tcl without mariaci.tcl caused the start step to
   emit 'max_wal_size=MB' (empty value) and fail pg_ctl. Move
   calc_redo_mb to src/generic/genci.tcl next to calc_buffer_pool_mb so
   it is available to every RDBMS port.

2. In postgresql_start the pg_ctl command was passed to 'bash -c'
   without escaping the embedded double quotes (used by -D/-l/-o),
   producing a Tcl list-parse error. Apply the same string map escape
   pattern used by every other 'open |bash -c' invocation in pgci.tcl.

Validated end-to-end on WSL Ubuntu 24.04 against postgres/postgres master:
  CLONE -> BUILD -> PACKAGE -> INSTALL -> INIT -> START ->
  PING -> CHANGE_PASSWORD -> TPROC-C OLTP -> SHUTDOWN all succeeded.
  Result: 71,999 NOPM / 165,731 PostgreSQL TPM (16 vusers).

Author: crprashant

src/generic/genci.tcl

@@ -1336,6 +1336,24 @@ proc calc_buffer_pool_mb {} {
     return $bp_mb
 }
 
+proc calc_redo_mb {} {
+    # derive from buffer pool
+    set bp_mb [calc_buffer_pool_mb]
+
+    if {$bp_mb <= 0} {
+        return 2048
+    }
+
+    # 25% of buffer pool
+    set redo_mb [expr {$bp_mb / 4}]
+
+    # range 2GB–32GB
+    if {$redo_mb < 2048}  { set redo_mb 2048 }
+    if {$redo_mb > 32768} { set redo_mb 32768 }
+
+    return $redo_mb
+}
+
 # watcher
 proc job_watcher {} {
     if {$::watcher_running} {

src/mariadb/mariaci.tcl

@@ -10,24 +10,6 @@ proc mariadb_ci_id {cidict refname} {
     return $ci_id
 }
 
-proc calc_redo_mb {} {
-    # derive from buffer pool
-    set bp_mb [calc_buffer_pool_mb]
-
-    if {$bp_mb <= 0} {
-        return 2048
-    }
-
-    # 25% of buffer pool
-    set redo_mb [expr {$bp_mb / 4}]
-
-    # range 2GB–32GB
-    if {$redo_mb < 2048}  { set redo_mb 2048 }
-    if {$redo_mb > 32768} { set redo_mb 32768 }
-
-    return $redo_mb
-}
-
 proc mariadb_ci_safe_ref {refname} {
     # safe path part
     return [string map {/ _} $refname]

src/postgresql/pgci.tcl

@@ -762,8 +762,9 @@ proc postgresql_start {cidict refname} {
     }
 
     set ::pipe_done 0
+    set shell_safe_cmd [string map {\" \\\"} $full_cmd]
     if {[catch {
-        set pipe [open "|bash -c \"$full_cmd\"" "r"]
+        set pipe [open "|bash -c \"$shell_safe_cmd\"" "r"]
         fconfigure $pipe -blocking 0 -buffering line
         fileevent $pipe readable [list handle_output $pipe]
         after 30000 {set ::pipe_done 1}