chore: replace dotenv with dotenvy (#2003)

* chore: replace `dotenv` with `dotenvy`

The former appears to be unmaintained and the latter is a drop-in replacement.

* chore: fix all warnings

sqlx-cli/src/bin/cargo-sqlx.rs

@@ -1,6 +1,5 @@
 use clap::Parser;
 use console::style;
-use dotenv::dotenv;
 use sqlx_cli::Opt;
 use std::process;
 
@@ -14,7 +13,7 @@ enum Cli {
 
 #[tokio::main]
 async fn main() {
-    dotenv().ok();
+    dotenvy::dotenv().ok();
     let Cli::Sqlx(opt) = Cli::parse();
 
     if let Err(error) = sqlx_cli::run(opt).await {

sqlx-cli/src/bin/sqlx.rs

@@ -1,11 +1,10 @@
 use clap::Parser;
 use console::style;
-use dotenv::dotenv;
 use sqlx_cli::Opt;
 
 #[tokio::main]
 async fn main() {
-    dotenv().ok();
+    dotenvy::dotenv().ok();
     // no special handling here
     if let Err(error) = sqlx_cli::run(Opt::parse()).await {
         println!("{} {}", style("error:").bold().red(), error);