perf(query): reduce user query duration (#10037)

# Which Problems Are Solved

The resource usage to query user(s) on the database was high and
therefore could have performance impact.

# How the Problems Are Solved

Database queries involving the users and loginnames table were improved
and an index was added for user by email query.

# Additional Changes

- spellchecks
- updated apis on load tests

# additional info

needs cherry pick to v3

(cherry picked from commit 4df138286b)

internal/query/projection/user.go

@@ -124,6 +124,7 @@ func (*userProjection) Init() *old_handler.Check {
 			handler.NewPrimaryKey(HumanUserInstanceIDCol, HumanUserIDCol),
 			UserHumanSuffix,
 			handler.WithForeignKey(handler.NewForeignKeyOfPublicKeys()),
+			handler.WithIndex(handler.NewIndex("email", []string{HumanUserInstanceIDCol, "LOWER(" + HumanEmailCol + ")"})),
 		),
 		handler.NewSuffixedTable([]*handler.InitColumn{
 			handler.NewColumn(MachineUserIDCol, handler.ColumnTypeText),