Added Sequence Operations, selector and test cases

[Vishalk91-4]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y

re #2

2. What is the scope of this PR (e.g. component or file name):

• grammar.js
• expr.txt
• assign.txt
• schema.txt
• grammar.json
• parser.c

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

• Adding sequence operations
• Adding selectors
• Adding select_suffix syntax
• Adding Test Cases for selector expression and sequence operations

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

[Peefy]

Put x + y into the binary expression grammar and consider x - y, x * y, and x ** y, etc, as well as their priorities.

[Vishalk91-4]

In Binary expression I found that it already has x+y, x-y, x*y, x**y
So, Do you want me to add binary_operator inside sequence_operation inplace of concatenation to cover it all

[Peefy]

Ok, you can remove concatenation here.

[Peefy]

LGTM