Add YAML fixtures for Regexp encoding options

Author: andrykonchin

spec/truffle/parsing/fixtures/regexps/encoding_options/with_e_option.yaml

@@ -0,0 +1,12 @@
+subject: "Regexp"
+description: "encoding options / with e option"
+note: >
+  The 'e' modifiers overrides source encoding with EUC-JP encoding
+focused_on_node: "org.truffleruby.language.literal.ObjectLiteralNode"
+ruby: |
+  /abc/e
+ast: |
+  ObjectLiteralNode
+      attributes:
+          flags = 1
+          object = RubyRegexp(source = abc, options = RegexpOptions(kcode: EUC, fixed, literal), encoding = EUC-JP)

spec/truffle/parsing/fixtures/regexps/encoding_options/with_n_option.yaml

@@ -0,0 +1,13 @@
+subject: "Regexp"
+description: "encoding options / with n option"
+note: >
+  The 'n' modifiers overrides source encoding with US-ASCII encoding.
+  According to the documentation it should be ASCII-8BIT encoding actually.
+focused_on_node: "org.truffleruby.language.literal.ObjectLiteralNode"
+ruby: |
+  /abc/n
+ast: |
+  ObjectLiteralNode
+      attributes:
+          flags = 1
+          object = RubyRegexp(source = abc, options = RegexpOptions(kcode: NONE, encodingNone, literal), encoding = US-ASCII)

spec/truffle/parsing/fixtures/regexps/encoding_options/with_s_option.yaml

@@ -0,0 +1,12 @@
+subject: "Regexp"
+description: "encoding options / with s option"
+note: >
+  The 's' modifiers overrides source encoding with Windows-31J encoding
+focused_on_node: "org.truffleruby.language.literal.ObjectLiteralNode"
+ruby: |
+  /abc/s
+ast: |
+  ObjectLiteralNode
+      attributes:
+          flags = 1
+          object = RubyRegexp(source = abc, options = RegexpOptions(kcode: SJIS, fixed, literal), encoding = Windows-31J)

spec/truffle/parsing/fixtures/regexps/encoding_options/with_u_option.yaml

@@ -0,0 +1,12 @@
+subject: "Regexp"
+description: "encoding options / with u option"
+note: >
+  The 'u' modifiers overrides source encoding with UTF-8 encoding
+focused_on_node: "org.truffleruby.language.literal.ObjectLiteralNode"
+ruby: |
+  /abc/u
+ast: |
+  ObjectLiteralNode
+      attributes:
+          flags = 1
+          object = RubyRegexp(source = abc, options = RegexpOptions(kcode: UTF8, fixed, literal), encoding = UTF-8)