improve description of --flamechart and --flamegraph (#8917)

improve description of --flamechart and --flamegraph, explaining the difference

Author: qiweiii

crates/forge/bin/cmd/test/mod.rs

@@ -86,10 +86,16 @@ pub struct TestArgs {
     debug: Option<Regex>,
 
     /// Generate a flamegraph for a single test. Implies `--decode-internal`.
+    ///
+    /// A flame graph is used to visualize which functions or operations within the smart contract
+    /// are consuming the most gas overall in a sorted manner.
     #[arg(long, conflicts_with = "flamechart")]
     flamegraph: bool,
 
     /// Generate a flamechart for a single test. Implies `--decode-internal`.
+    ///
+    /// A flame chart shows the gas usage over time, illustrating when each function is
+    /// called (execution order) and how much gas it consumes at each point in the timeline.
     #[arg(long, conflicts_with = "flamegraph")]
     flamechart: bool,