Handle implicit aliases in projection SELECT column parsing

Projection column lists like `SELECT name, max(frequency) max_frequency`
need to handle implicit aliases where an identifier follows an expression
without the AS keyword. This adds parseImplicitAlias call after parsing
each column expression in projections.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

parser/parser.go

@@ -8006,6 +8006,8 @@ func (p *Parser) parseProjection() *ast.Projection {
 
 		col := p.parseExpression(LOWEST)
 		if col != nil {
+			// Handle implicit alias (identifier without AS)
+			col = p.parseImplicitAlias(col)
 			proj.Select.Columns = append(proj.Select.Columns, col)
 		}
 

parser/testdata/01710_projections/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt2": true
-  }
-}
+{}

parser/testdata/01710_projections_in_distributed_query/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}

parser/testdata/02796_projection_date_filter_on_view/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true
-  }
-}
+{}

parser/testdata/03230_system_projections/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true
-  }
-}
+{}