[Refactor] call generate_ir according to is_compiable

[fzhedu]

Why I'm doing:

call generate_ir_imp directly even it isn't compilable, would generate wrong ir.

What I'm doing:

call generate_ir_imp according to whether the expr is compiable.

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 3.2
  • 3.1
  • 3.0
  • 2.5

[github-actions]

[FE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[BE Incremental Coverage Report]

❌ fail : 18 / 24 (75.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	be/src/exprs/binary_predicate.cpp	0	4	00.00%	[123, 124, 391, 392]
🔵	be/src/exprs/arithmetic_expr.cpp	7	9	77.78%	[336, 337]
🔵	be/src/exprs/case_expr.cpp	5	5	100.00%	[]
🔵	be/src/exprs/cast_expr.cpp	1	1	100.00%	[]
🔵	be/src/exprs/expr.cpp	4	4	100.00%	[]
🔵	be/src/exprs/jit/jit_engine.cpp	1	1	100.00%	[]