add workflow tests for comparison checks

testdata/err/invalid_comparisons.out

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+test.yaml:16:17: "string" value cannot be compared to "{}" value with "==" operator [expression]
+test.yaml:18:17: "number" value cannot be compared to "array<bool>" value with "!=" operator [expression]
+test.yaml:20:17: "array<bool>" value cannot be compared to "array<{}>" value with "==" operator [expression]
+test.yaml:22:17: "number" value cannot be compared to "null" value with ">" operator [expression]
+test.yaml:24:17: "bool" value cannot be compared to "bool" value with "<" operator [expression]
+test.yaml:26:17: "string" value cannot be compared to "{}" value with ">=" operator [expression]
+test.yaml:28:17: "bool" value cannot be compared to "array<bool>" value with "<=" operator [expression]

testdata/err/invalid_comparisons.yaml

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+on: push
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        o:
+          - {}
+        a:
+          - [true]
+        a2:
+          - [{}]
+    steps:
+      - run: echo 'comparing == to object with implicit conversion is not allowed'
+        if: ${{ 'foo' == matrix.o }}
+      - run: echo 'comparing != to array with implicit conversion is not allowed'
+        if: ${{ 42 != matrix.a }}
+      - run: echo 'comparing == array and incompatible array is not allowed'
+        if: ${{ matrix.a == matrix.a2 }}
+      - run: echo 'comparing > to null is not allowed'
+        if: ${{ 1 > null }}
+      - run: echo 'comparing > to bool is not allowed'
+        if: ${{ false < true }}
+      - run: echo 'comparing >= to object is not allowed'
+        if: ${{ 'foo' >= matrix.o }}
+      - run: echo 'comparing <= to array is not allowed'
+        if: ${{ false <= matrix.a }}

testdata/ok/valid_comparisons.yaml

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+on: push
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        o:
+          - {}
+        a:
+          - [true]
+    steps:
+      - run: echo 'string is converted to number implicitly'
+        if: ${{ '42' == 42 }}
+      - run: echo 'bool is converted to number implicitly'
+        if: ${{ true == 1 }}
+      - run: echo 'null is converted to number implicitly'
+        if: ${{ null == 0 }}
+      - run: echo 'string and bool implicit conversions are allowed though it is problematic'
+        if: ${{ '1' == true }}
+      - run: echo 'string and null implicit conversions are allowed though it is problematic'
+        if: ${{ '0' == null }}
+      - run: echo 'comparing null to any value is allowed'
+        if: ${{ null == matrix.o }}
+      - run: echo 'comparing object to object is allowed'
+        if: ${{ matrix.o == matrix.o }}
+      - run: echo 'comparing object to object is allowed'
+        if: ${{ matrix.a == matrix.a }}
+      - run: echo 'string is converted to number implicitly on <'
+        if: ${{ '41' < 42 }}