Refactor Filter

[William-Young-97]

Please provide a brief description of the change.

• Add .Filter for iterator method chaining, except for: iter.go, lines.go, map.go and zip.go

Which issue does this change relate to?

#59

Contribution checklist.

Replace the space in each box with "X" to check it off.

• [X] I have read and understood the CONTRIBUTING guidelines
• [X] My code is formatted (make check)
• [X] I have run tests (make test)
• [X] All commits in my PR conform to the commit hygiene section
• [X] I have added relevant tests
• [X] I have not added any dependencies

Additional context

Unsure how whether about the mentioned methods that haven't been done due to .Filter being constrained to Integers. Unsure about whether a generic Filter[T] function needs to be added to iter.go

[BooleanCat]

@William-Young-97 I've run the tests so you can see if there are any problems I missed.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (d6bd636) 100.00% compared to head (556d580) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #71 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 20 20 Lines 579 599 +20 ========================================= + Hits 579 599 +20 ``` | [Files Changed](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin) | Coverage Δ | | |---|---|---| | [iter/chain.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9jaGFpbi5nbw==) | `100.00% <100.00%> (ø)` | | | [iter/channel.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9jaGFubmVsLmdv) | `100.00% <100.00%> (ø)` | | | [iter/counter.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9jb3VudGVyLmdv) | `100.00% <100.00%> (ø)` | | | [iter/cycle.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9jeWNsZS5nbw==) | `100.00% <100.00%> (ø)` | | | [iter/drop.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9kcm9wLmdv) | `100.00% <100.00%> (ø)` | | | [iter/exhausted.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9leGhhdXN0ZWQuZ28=) | `100.00% <100.00%> (ø)` | | | [iter/filter.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9maWx0ZXIuZ28=) | `100.00% <100.00%> (ø)` | | | [iter/lift.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9saWZ0Lmdv) | `100.00% <100.00%> (ø)` | | | [iter/repeat.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci9yZXBlYXQuZ28=) | `100.00% <100.00%> (ø)` | | | [iter/take.go](https://app.codecov.io/gh/BooleanCat/go-functional/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Godkin#diff-aXRlci90YWtlLmdv) | `100.00% <100.00%> (ø)` | |

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