fix: `--env` flag confusing message on syntax error (#23915)

Enhanced warning message for --env flag with run and eval subcommands. 

The commit is specifically made to address issue #23674 by improving the
warning messages that appear when using the --env flag with run or eval
subcommands in the following scenarios:

1. Missing environment file.
2. Incorrect syntax in the environment file content.


**Changes made**

- Distinguishes between cases of missing environment file and wrong
syntax in the environment file content.
- Shows a concise warning message to convey the case/issue occurred.

**Code changes & enhancements**
- Implemented a match statement to handle different types of errors
received while getting and parsing the file content to display a concise
warning message, rather than simple error check and then displaying the
same warning message for whatever the type of error is.
- Updated the related existing tests to reflect the new warning
messages.
- Added two test cases to cover the wrong environment file content
syntax with both run and eval subcommands.

**Impact**
The use of --env flag with both run/eval would be more user-friendly as
it gives a precise description of what is not right when using
incorrectly.

If you could give it a look, @dsherret , I appreciate your feedback on
these changes.

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/specs/run/env_unparsable_file/main.out b/tests/specs/run/env_unparsable_file/main.out
new file mode 100644
index 000000000..a19ff4dd6
--- /dev/null
+++ b/tests/specs/run/env_unparsable_file/main.out
@@ -0,0 +1,4 @@
+Warning Parsing failed within the specified environment file: ../../../testdata/env_unparsable at index: 3 of the value: c:\path
+valid
+undefined
+undefined