Add expected value field in all assert Error Message

[fabricereix]

Currently, the expected value is taken from the input Hurl file
for example

error: Assert body value
  --> tests_failed/assert_base64.hurl:12:8
   |
   | GET http://localhost:8000/error-assert-base64
   | ...
12 | base64,bGluZTEKbGluZTIKbGluZTMK;
   |        ^^^^^^^^^^^^^^^^^^^^^^^^ actual value is <hex, 6c696e65310a6c696e65320d0a6c696e65330a;>
   |

Display the expected value along the actual value using the same format.

error: Assert body value
  --> tests_failed/assert_base64.hurl:12:8
   |
   | GET http://localhost:8000/error-assert-base64
   | ...
12 | base64,bGluZTEKbGluZTIKbGluZTMK;
   |        ^^^^^^^^^^^^^^^^^^^^^^^^ expected: <hex, 6c696e65310a6c696e65320d0a6c696e65330a;>
   |                                 actual:   <hex, 6c696e65310a6c696e65320d0a00696e6533;>
   |

[jcamiel]

Another possibiliy:

error: Assert body value
  --> tests_failed/assert_base64.hurl:12:8
   |
   | GET http://localhost:8000/error-assert-base64
   | ...
12 | base64,bGluZTEKbGluZTIKbGluZTMK;
   |        ^^^^^^^^^^^^^^^^^^^^^^^^
   |   actual:   <hex, 6c696e65310a6c696e65320d0a00696e6533;>
   |   expected: <hex, 6c696e65310a6c696e65320d0a6c696e65330a;>
   |

To be like explicit asserts

[fabricereix]

We can indeed try to display for all the assert errors:

• the exact line in the input Hurl file with its line number. This is the context. It can contain variables and Hurl escaping.
• the expected/actual values

Example for the diff assert errors:

error: Assert body value
  --> test.hurl:8:1
   |
   | GET http://localhost:8000/test
   | ...
 8 |   "age": {{age}}
   |     -  "age": 27,
   |     +  "age": 28,
   |

error: Assert body value
  --> test.hurl:8:1
   |
   | GET http://localhost:8000/test
   | ...
 8 |   "g_clef": "\uD834\uDD1E",
   |     -  "g_clef": 𝄞,
   |     +  "f_clef": 𝄢,
   |