Reference: #307

This change fixes the source of the `bcrypt_hash` generation to being the result of the random password generation. The issue was introduced in v3.4.0.

Previously:

```
--- FAIL: TestAccResourcePassword_BcryptHash (0.63s)
    /Users/bflad/src/github.com/hashicorp/terraform-provider-random/internal/provider/resource_password_test.go:107: Step 1/1 error: Check failed: Check 3/3 error: crypto/bcrypt: hashedPassword is not the hash of the given password
```

Suggested CHANGELOG:

```
NOTES:

* resource/random_password: If the resource was created between versions 3.4.0 and 3.4.2, the `bcrypt_hash` value will not correctly verify against the `result` value. Use `terraform taint` or `terraform apply -replace` to trigger resource recreation with this version.

BUG FIXES:

* resource/random_password: Fixed incorrect `bcrypt_hash` generation since version 3.4.0
```

…hash

… from 3.3.2

Reference: #306

This fixes the `override_special` attribute issues by removing `Computed: true` and the empty string default value plan modifier (this attribute's value should always come from the practitioner) and resolves the underlying issue of always reading `plan.OverrideSpecial.Value` into the state, which will never be correct for null configurations.

For any environment that happened to upgrade to 3.4.2 and save the empty string into state, the replacement plan modifier will allow in-place modification from empty string (`""`) to `null`.

Previously after removing `Computed: true` and default value plan modifier:

```
=== CONT  TestAccResourcePassword_OverrideSpecial_FromVersion3_3_2
    resource_password_test.go:221: Step 2/2 error: Error running apply: exit status 1

        Error: Provider produced inconsistent result after apply

        When applying changes to random_password.test, provider
        "provider[\"registry.terraform.io/hashicorp/random\"]" produced an unexpected
        new value: .override_special: was null, but now cty.StringVal("").

        This is a bug in the provider, which should be reported in the provider's own
        issue tracker.
=== CONT  TestAccResourcePassword_OverrideSpecial_FromVersion3_4_2
    resource_password_test.go:255: Step 2/2 error: Error running apply: exit status 1

        Error: Provider produced inconsistent result after apply

        When applying changes to random_password.test, provider
        "provider[\"registry.terraform.io/hashicorp/random\"]" produced an unexpected
        new value: .override_special: was null, but now cty.StringVal("").

        This is a bug in the provider, which should be reported in the provider's own
        issue tracker.
```

Previously before adjusting requires replace plan modifier:

```
=== CONT  TestAccResourcePassword_OverrideSpecial_FromVersion3_3_2
    resource_password_test.go:221: Step 2/2 error: Check failed: Check 3/3 error: attribute values are different, got :i$(*K3_Vinv and FSw{$8sB#Uc3
=== CONT  TestAccResourcePassword_OverrideSpecial_FromVersion3_4_2
    resource_password_test.go:255: Step 2/2 error: Check failed: Check 3/3 error: attribute values are different, got VrNYb]{#Z2Xu and XZD#_<BjDhkH
```

Co-authored-by: Benjamin Bennett <ben.bennett@hashicorp.com>

…ial explicitly to null during import

Previously:

```
=== RUN   TestAccResourcePassword
    resource_password_test.go:67: ImportStateVerify attributes not equivalent. Difference is shown below. Top is actual, bottom is expected.

        (map[string]string) (len=1) {
         (string) (len=16) "override_special": (string) ""
        }

        (map[string]string) {
        }
--- FAIL: TestAccResourcePassword (0.79s)
```