Int64 AtLeast, AtMost and Between validators

[ewbankkit]

Closes #2.

Based on https://github.com/hashicorp/terraform-provider-awscc/tree/main/internal/validate.

% go test -v ./int64validator
=== RUN   TestAtLeastValidator
=== PAUSE TestAtLeastValidator
=== RUN   TestAtMostValidator
=== PAUSE TestAtMostValidator
=== RUN   TestBetweenValidator
=== PAUSE TestBetweenValidator
=== CONT  TestAtLeastValidator
=== CONT  TestBetweenValidator
=== RUN   TestAtLeastValidator/valid_integer_as_Int64_min
=== CONT  TestAtMostValidator
=== RUN   TestBetweenValidator/valid_integer_as_Int64_max
=== RUN   TestAtMostValidator/not_an_Int64
=== RUN   TestAtMostValidator/unknown_Int64
=== RUN   TestAtLeastValidator/too_small_integer_as_Int64
=== RUN   TestBetweenValidator/too_small_integer_as_Int64
=== RUN   TestAtMostValidator/null_Int64
=== RUN   TestBetweenValidator/too_large_integer_as_Int64
=== RUN   TestAtLeastValidator/not_an_Int64
=== RUN   TestAtLeastValidator/unknown_Int64
=== RUN   TestAtMostValidator/valid_integer_as_Int64
=== RUN   TestAtLeastValidator/null_Int64
=== RUN   TestBetweenValidator/not_an_Int64
=== RUN   TestAtLeastValidator/valid_integer_as_Int64
=== RUN   TestBetweenValidator/unknown_Int64
--- PASS: TestAtLeastValidator (0.00s)
    --- PASS: TestAtLeastValidator/valid_integer_as_Int64_min (0.00s)
    --- PASS: TestAtLeastValidator/too_small_integer_as_Int64 (0.00s)
    --- PASS: TestAtLeastValidator/not_an_Int64 (0.00s)
    --- PASS: TestAtLeastValidator/unknown_Int64 (0.00s)
    --- PASS: TestAtLeastValidator/null_Int64 (0.00s)
    --- PASS: TestAtLeastValidator/valid_integer_as_Int64 (0.00s)
=== RUN   TestAtMostValidator/valid_integer_as_Int64_min
=== RUN   TestBetweenValidator/null_Int64
=== RUN   TestBetweenValidator/valid_integer_as_Int64
=== RUN   TestAtMostValidator/too_large_integer_as_Int64
=== RUN   TestBetweenValidator/valid_integer_as_Int64_min
--- PASS: TestAtMostValidator (0.00s)
    --- PASS: TestAtMostValidator/not_an_Int64 (0.00s)
    --- PASS: TestAtMostValidator/unknown_Int64 (0.00s)
    --- PASS: TestAtMostValidator/null_Int64 (0.00s)
    --- PASS: TestAtMostValidator/valid_integer_as_Int64 (0.00s)
    --- PASS: TestAtMostValidator/valid_integer_as_Int64_min (0.00s)
    --- PASS: TestAtMostValidator/too_large_integer_as_Int64 (0.00s)
--- PASS: TestBetweenValidator (0.00s)
    --- PASS: TestBetweenValidator/valid_integer_as_Int64_max (0.00s)
    --- PASS: TestBetweenValidator/too_small_integer_as_Int64 (0.00s)
    --- PASS: TestBetweenValidator/too_large_integer_as_Int64 (0.00s)
    --- PASS: TestBetweenValidator/not_an_Int64 (0.00s)
    --- PASS: TestBetweenValidator/unknown_Int64 (0.00s)
    --- PASS: TestBetweenValidator/null_Int64 (0.00s)
    --- PASS: TestBetweenValidator/valid_integer_as_Int64 (0.00s)
    --- PASS: TestBetweenValidator/valid_integer_as_Int64_min (0.00s)
PASS
ok  	github.com/hashicorp/terraform-plugin-framework-validators/int64validator	0.730s

[bflad]

Looks great, thanks @ewbankkit! 🚀

[github-actions]

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