getter function for http base class in api handler

[KensukeTakahara]

this fixies #2327.

This bug is caused by next.js PR #32999 (included in next v12.0.9).
I implemented the getter function of event.req & event.res.

Or should I update next.js v11.1.2 to v12 in packages/libs/core/package.json?

[slsnextbot]

Handler Size Report

No changes to handler sizes.

Base Handler Sizes (kB) (commit ecb03a6)

{
    "Lambda": {
        "Default Lambda": {
            "Standard": 1524,
            "Minified": 668
        },
        "Image Lambda": {
            "Standard": 1488,
            "Minified": 800
        }
    },
    "Lambda@Edge": {
        "Default Lambda": {
            "Standard": 1534,
            "Minified": 673
        },
        "Default Lambda V2": {
            "Standard": 1526,
            "Minified": 670
        },
        "API Lambda": {
            "Standard": 634,
            "Minified": 318
        },
        "Image Lambda": {
            "Standard": 1496,
            "Minified": 805
        },
        "Regeneration Lambda": {
            "Standard": 1187,
            "Minified": 546
        },
        "Regeneration Lambda V2": {
            "Standard": 1253,
            "Minified": 573
        }
    }
}

New Handler Sizes (kB) (commit b3a8171)

{
    "Lambda": {
        "Default Lambda": {
            "Standard": 1524,
            "Minified": 668
        },
        "Image Lambda": {
            "Standard": 1488,
            "Minified": 800
        }
    },
    "Lambda@Edge": {
        "Default Lambda": {
            "Standard": 1534,
            "Minified": 673
        },
        "Default Lambda V2": {
            "Standard": 1526,
            "Minified": 670
        },
        "API Lambda": {
            "Standard": 634,
            "Minified": 318
        },
        "Image Lambda": {
            "Standard": 1496,
            "Minified": 805
        },
        "Regeneration Lambda": {
            "Standard": 1187,
            "Minified": 546
        },
        "Regeneration Lambda V2": {
            "Standard": 1253,
            "Minified": 573
        }
    }
}

[codecov]

Codecov Report

Merging #2344 (b3a8171) into master (ecb03a6) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2344      +/-   ##
==========================================
+ Coverage   83.55%   83.58%   +0.02%     
==========================================
  Files         102      102              
  Lines        3679     3685       +6     
  Branches     1176     1178       +2     
==========================================
+ Hits         3074     3080       +6     
  Misses        593      593              
  Partials       12       12              

Impacted Files	Coverage Δ
packages/libs/core/src/handle/api.ts	100.00% <100.00%> (ø)

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