Handle decimal subnormal and underflow cases

[gabilang]

Purpose

This PR treats the decimal subnormal values as Zero according to IEEE-754 Decimal specification.

Fixes #38082

Approach

The absolute decimal values smaller than the minimum positive normal decimal value are treated as decimal value zero.

Samples

Remarks

Check List

• [x] Read the Contributing Guide
• [ ] Updated Change Log
• [ ] Checked Tooling Support (#<Issue Number>)
• [ ] Added necessary tests
  • [x] Unit Tests
  • [ ] Spec Conformance Tests
  • [ ] Integration Tests
  • [ ] Ballerina By Example Tests
• [ ] Increased Test Coverage
• [ ] Added necessary documentation
  • [ ] API documentation
  • [ ] Module documentation in Module.md files
  • [ ] Ballerina By Examples

[codecov[bot]]

Codecov Report

Base: 76.70% // Head: 76.72% // Increases project coverage by +0.01% :tada:

Coverage data is based on head (1e02dce) compared to base (2c5023c). Patch coverage: 93.24% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #38172      +/-   ##
============================================
+ Coverage     76.70%   76.72%   +0.01%     
- Complexity    53056    53065       +9     
============================================
  Files          3356     3356              
  Lines        199240   199224      -16     
  Branches      25820    25817       -3     
============================================
+ Hits         152832   152850      +18     
+ Misses        37778    37745      -33     
+ Partials       8630     8629       -1     

Impacted Files	Coverage Δ
.../org/ballerinalang/langlib/decimal/FromString.java	85.71% <ø> (-4.29%)	:arrow_down:
...inalang/formatter/core/FormattingTreeModifier.java	95.83% <ø> (ø)
...testerina/natives/mock/GenericMockObjectValue.java	8.75% <ø> (ø)
...viders/context/ConstantDeclarationNodeContext.java	94.02% <50.00%> (ø)
.../providers/context/EnumDeclarationNodeContext.java	85.71% <50.00%> (ø)
...viders/context/ListenerDeclarationNodeContext.java	73.33% <50.00%> (ø)
...text/ModuleXMLNamespaceDeclarationNodeContext.java	89.18% <50.00%> (ø)
...eaction/providers/ExtractToLocalVarCodeAction.java	89.47% <80.00%> (ø)
...lerina/runtime/api/constants/RuntimeConstants.java	94.73% <100.00%> (ø)
...untime/internal/util/exceptions/RuntimeErrors.java	99.09% <100.00%> (+<0.01%)	:arrow_up:
... and 39 more

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[KavinduZoysa]

decimal d1 = 1.01e-6143d; Does this case a subnormal? With this change, the resut is 1.01E-6143, but for decimal d1 = 0.01e-6143d; it gives zero.

[gabilang]

decimal d1 = 1.01e-6143d; Does this case a subnormal? With this change, the resut is 1.01E-6143, but for decimal d1 = 0.01e-6143d; it gives zero.

Since the exponent of minimum representable magnitude of normal decimal value according to the spec is -6143, the value 0.01e-6143 is going to fall in subnormal range. So the value of 0.01e-6143d need to be treat as zero and 1.01e-6143d is a normal decimal value.