Enhance methods in SDK taking Blob to take impl Into<Blob> instead

[ysaito1001]

This issue tracks a complementary task for #3877.

The previous PR introduced conversions between Vec<u8> and Blob, as well as from &[u8] to Blob. However, these changes do not immediately improve the ergonomics of the following method call (example from kms):

src/types/_recipient_info.rs:    pub fn set_attestation_document(mut self, input: ::std::option::Option<::aws_smithy_types::Blob>) -> Self {

To enhance the ergonomics of call sites, this codegen update modifies the method signature to accept Option<impl Into<Blob>>.