SQL: Allow whitespaces in escape patterns (#47577)

Previously, we supported only the format `{fn <FUNCTION_NAME>()}`
but other DBs like MSSQL, DB2, MariaDB/MySQL alos allow whitespaces
between `{` and `fn`. Furhermore, also some applications - like PowerBI -
generate escape sequences with spaces: `select { fn name(params) } etc.`

Add support for white spaces between `{` and the escape pattern definition
like `fn`, `ts`, `d`, `guid` etc.

Closes: #47401

(cherry picked from commit 08a22d0)

x-pack/plugin/sql/src/main/antlr/SqlBase.g4

@@ -201,7 +201,7 @@ pattern
 
 patternEscape
     : ESCAPE escape=string
-    | ESCAPE_ESC escape=string '}'
+    | ESCAPE_ESC escape=string ESC_END
     ;
 
 valueExpression
@@ -255,7 +255,7 @@ extractTemplate
 
 functionExpression
     : functionTemplate
-    | FUNCTION_ESC functionTemplate '}'
+    | FUNCTION_ESC functionTemplate ESC_END
     ;
 
 functionTemplate
@@ -446,15 +446,16 @@ YEAR: 'YEAR';
 YEARS: 'YEARS';
 
 // Escaped Sequence
-ESCAPE_ESC: '{ESCAPE';
-FUNCTION_ESC: '{FN';
-LIMIT_ESC:'{LIMIT';
-DATE_ESC: '{D';
-TIME_ESC: '{T';
-TIMESTAMP_ESC: '{TS';
+ESCAPE_ESC: ESC_START 'ESCAPE';
+FUNCTION_ESC: ESC_START 'FN';
+LIMIT_ESC: ESC_START 'LIMIT';
+DATE_ESC: ESC_START 'D';
+TIME_ESC: ESC_START 'T';
+TIMESTAMP_ESC: ESC_START 'TS';
 // mapped to string literal
-GUID_ESC: '{GUID';
+GUID_ESC: ESC_START 'GUID';
 
+ESC_START: '{' (WS)*;
 ESC_END: '}';
 
 EQ  : '=';

x-pack/plugin/sql/src/main/antlr/SqlBase.tokens

@@ -96,35 +96,36 @@ DATE_ESC=95
 TIME_ESC=96
 TIMESTAMP_ESC=97
 GUID_ESC=98
-ESC_END=99
-EQ=100
-NULLEQ=101
-NEQ=102
-LT=103
-LTE=104
-GT=105
-GTE=106
-PLUS=107
-MINUS=108
-ASTERISK=109
-SLASH=110
-PERCENT=111
-CONCAT=112
-DOT=113
-PARAM=114
-STRING=115
-INTEGER_VALUE=116
-DECIMAL_VALUE=117
-IDENTIFIER=118
-DIGIT_IDENTIFIER=119
-TABLE_IDENTIFIER=120
-QUOTED_IDENTIFIER=121
-BACKQUOTED_IDENTIFIER=122
-SIMPLE_COMMENT=123
-BRACKETED_COMMENT=124
-WS=125
-UNRECOGNIZED=126
-DELIMITER=127
+ESC_START=99
+ESC_END=100
+EQ=101
+NULLEQ=102
+NEQ=103
+LT=104
+LTE=105
+GT=106
+GTE=107
+PLUS=108
+MINUS=109
+ASTERISK=110
+SLASH=111
+PERCENT=112
+CONCAT=113
+DOT=114
+PARAM=115
+STRING=116
+INTEGER_VALUE=117
+DECIMAL_VALUE=118
+IDENTIFIER=119
+DIGIT_IDENTIFIER=120
+TABLE_IDENTIFIER=121
+QUOTED_IDENTIFIER=122
+BACKQUOTED_IDENTIFIER=123
+SIMPLE_COMMENT=124
+BRACKETED_COMMENT=125
+WS=126
+UNRECOGNIZED=127
+DELIMITER=128
 '('=1
 ')'=2
 ','=3
@@ -216,25 +217,18 @@ DELIMITER=127
 'WITH'=89
 'YEAR'=90
 'YEARS'=91
-'{ESCAPE'=92
-'{FN'=93
-'{LIMIT'=94
-'{D'=95
-'{T'=96
-'{TS'=97
-'{GUID'=98
-'}'=99
-'='=100
-'<=>'=101
-'<'=103
-'<='=104
-'>'=105
-'>='=106
-'+'=107
-'-'=108
-'*'=109
-'/'=110
-'%'=111
-'||'=112
-'.'=113
-'?'=114
+'}'=100
+'='=101
+'<=>'=102
+'<'=104
+'<='=105
+'>'=106
+'>='=107
+'+'=108
+'-'=109
+'*'=110
+'/'=111
+'%'=112
+'||'=113
+'.'=114
+'?'=115

x-pack/plugin/sql/src/main/antlr/SqlBaseLexer.tokens

@@ -96,34 +96,35 @@ DATE_ESC=95
 TIME_ESC=96
 TIMESTAMP_ESC=97
 GUID_ESC=98
-ESC_END=99
-EQ=100
-NULLEQ=101
-NEQ=102
-LT=103
-LTE=104
-GT=105
-GTE=106
-PLUS=107
-MINUS=108
-ASTERISK=109
-SLASH=110
-PERCENT=111
-CONCAT=112
-DOT=113
-PARAM=114
-STRING=115
-INTEGER_VALUE=116
-DECIMAL_VALUE=117
-IDENTIFIER=118
-DIGIT_IDENTIFIER=119
-TABLE_IDENTIFIER=120
-QUOTED_IDENTIFIER=121
-BACKQUOTED_IDENTIFIER=122
-SIMPLE_COMMENT=123
-BRACKETED_COMMENT=124
-WS=125
-UNRECOGNIZED=126
+ESC_START=99
+ESC_END=100
+EQ=101
+NULLEQ=102
+NEQ=103
+LT=104
+LTE=105
+GT=106
+GTE=107
+PLUS=108
+MINUS=109
+ASTERISK=110
+SLASH=111
+PERCENT=112
+CONCAT=113
+DOT=114
+PARAM=115
+STRING=116
+INTEGER_VALUE=117
+DECIMAL_VALUE=118
+IDENTIFIER=119
+DIGIT_IDENTIFIER=120
+TABLE_IDENTIFIER=121
+QUOTED_IDENTIFIER=122
+BACKQUOTED_IDENTIFIER=123
+SIMPLE_COMMENT=124
+BRACKETED_COMMENT=125
+WS=126
+UNRECOGNIZED=127
 '('=1
 ')'=2
 ','=3
@@ -215,25 +216,18 @@ UNRECOGNIZED=126
 'WITH'=89
 'YEAR'=90
 'YEARS'=91
-'{ESCAPE'=92
-'{FN'=93
-'{LIMIT'=94
-'{D'=95
-'{T'=96
-'{TS'=97
-'{GUID'=98
-'}'=99
-'='=100
-'<=>'=101
-'<'=103
-'<='=104
-'>'=105
-'>='=106
-'+'=107
-'-'=108
-'*'=109
-'/'=110
-'%'=111
-'||'=112
-'.'=113
-'?'=114
+'}'=100
+'='=101
+'<=>'=102
+'<'=104
+'<='=105
+'>'=106
+'>='=107
+'+'=108
+'-'=109
+'*'=110
+'/'=111
+'%'=112
+'||'=113
+'.'=114
+'?'=115