Add support to replace directive in go.mod

[shravankshenoy]

Fixes #3492

About replace directive in go.mod

Replaces the content of a module at a specific version (or all versions) with another module version or with a local directory. Syntax as shown below

replace module-path [module-version] => replacement-path [replacement-version]

Detailed info at https://go.dev/doc/modules/gomod-ref

Changes made

• Added regex to get module-path, module-version, replacement-path and replacement-version from replace directive
• Wrote conditions to handle single line and multi line replace directives
• Reran opencensus test to account for the replace directive
• Added new test using milvus go.mod to test the replace directive functionality `

[AyanSinhaMahapatra]

@shravankshenoy gentle ping