minor #25585 Add type string to docblock for Process::setInput() (icanhazstring)

This PR was submitted for the 3.4 branch but it was squashed and merged into the 3.3 branch instead (closes #25585).

Discussion
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Add type string to docblock for Process::setInput()

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

Add `string` as valid `$input` for `Process::setInput()`. Since `getInput()` will also return as string and the internal method `ProcessUtils::validateInput()` will accept a string, this should be a viable input type.

Commits
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e3de68f2 Add type string to docblock for Process::setInput()

Author: nicolas-grekas

Encoder/EncoderInterface.php

@@ -27,7 +27,7 @@ interface EncoderInterface
      * @param string $format  Format name
      * @param array  $context Options that normalizers/encoders have access to
      *
-     * @return scalar
+     * @return string|int|float|bool
      *
      * @throws UnexpectedValueException
      */

Normalizer/DenormalizableInterface.php

@@ -27,12 +27,12 @@ interface DenormalizableInterface
      * It is important to understand that the denormalize() call should denormalize
      * recursively all child objects of the implementor.
      *
-     * @param DenormalizerInterface $denormalizer The denormalizer is given so that you
-     *                                            can use it to denormalize objects contained within this object
-     * @param array|scalar          $data         The data from which to re-create the object
-     * @param string|null           $format       The format is optionally given to be able to denormalize differently
-     *                                            based on different input formats
-     * @param array                 $context      Options for denormalizing
+     * @param DenormalizerInterface       $denormalizer The denormalizer is given so that you
+     *                                                  can use it to denormalize objects contained within this object
+     * @param array|string|int|float|bool $data         The data from which to re-create the object
+     * @param string|null                 $format       The format is optionally given to be able to denormalize
+     *                                                  differently based on different input formats
+     * @param array                       $context      Options for denormalizing
      *
      * @return object
      */

Normalizer/NormalizableInterface.php

@@ -33,7 +33,7 @@ interface NormalizableInterface
      *                                        based on different output formats
      * @param array               $context    Options for normalizing this object
      *
-     * @return array|scalar
+     * @return array|string|int|float|bool
      */
     public function normalize(NormalizerInterface $normalizer, $format = null, array $context = array());
 }

Normalizer/NormalizerInterface.php

@@ -29,7 +29,7 @@ interface NormalizerInterface
      * @param string $format  Format the normalization result will be encoded as
      * @param array  $context Context options for the normalizer
      *
-     * @return array|scalar
+     * @return array|string|int|float|bool
      *
      * @throws InvalidArgumentException   Occurs when the object given is not an attempted type for the normalizer
      * @throws CircularReferenceException Occurs when the normalizer detects a circular reference when no circular