fix: Added support for --env for the compile subcommand

[HasanAlrimawi]

Supported the use of --env flag with the compile subcommand, so that the generated executable/binary file can access the passed env file.

The commit is made to address issue #22105 .

Use-case
deno compile --env=some_env_file file_using_env_vars.js -> executable/binary file "file_using_env_vars" is created.
file_using_env_vars to run it.

The problem that prevented the generated executable from finding the env file's environment variables

• Through the compile subcommand flow, CliOptions are made by CliOptions::new and so is the env file passed.
• Within the same function, environment variables found in the env file were loaded using the dotenvy crate which uses the std::env::set_var.
• The std::env::set_var sets the env variables exclusively for the currently running process, and thus the env variables loaded within compile time are exclusive for the operation itself "The compile operation".
• When you try to run the generated executable file, then a new process will take the responsibility, and this process doesn't have the environment variables loaded.

Solution of the problem
Pass the environment file to the executable/binary file, then load the environment variables whenever the file is ran.

Code changes

A) Added an attribute to hold the environment file name to Metadata struct within deno/cli/standalone/binary.rs, since the metadata is passed to the binary file by fn write_standalone_binary().

B) Added a getter for the environment file name to the CliOptions methods, since the Flags attribute that holds env_file attribute is private.

C) Added fn load_env_variables_from_env_file() to deno/cli/mainrt.rs which will be responsible for loading the env variables from the environment file at execution time.

@dsherret
@littledivy

[dsherret]

The code for this already exists elsewhere. Maybe it should be extracted out to a common function and reused here?

[HasanAlrimawi]

Hello @dsherret ,
Code has been wrapped within function to reuse.
Checks can be triggered.